Method and apparatus for recording and reproducing information on and from optical disc

ABSTRACT

An apparatus for recording and reproducing an information signal on and from an optical disc includes a memory. The information signal is written into the memory. The information signal is read out from the memory. An optical head generates a laser beam in response to the readout information signal, and applies the laser beam to the optical disc to record the readout information signal on the optical disc. A test signal is recorded on a position of the optical disc near a recording position thereof via the optical head during the writing of the information signal into the memory. The test signal is reproduced from the optical disc. The reproduced test signal is evaluated to generate an evaluation result. An intensity of the laser beam is optimized in response to the evaluation result.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to an apparatus for recording andreproducing information on and from an optical disc. In addition, thisinvention relates to a method of recording and reproducing informationon and from an optical disc. Furthermore, this invention relates to anoptical disc.

[0003] 2. Description of the Related Art

[0004] Optical discs contain an MD (Mini Disc). MD players includeshock-proof memories having a capacity of 4 MB which corresponds to aplayback time of about 10 seconds. During the playback mode of operationof the MD player, a pickup sequentially accesses sectors on an MD andreproduces data therefrom. In the MD player, the reproduced data aretemporarily stored in the shock-proof memory and are read out therefromso that the contents of the data are played back. When the pickup jumpsfrom a sector to a next sector, the pickup does not reproduce any datafrom the MD. Thus, during the playback mode of operation of the MDplayer, the reproduction of data from the MD by the pickup is sometimesinterrupted for a short time. The shock-proof memory absorbs such aninterruption of the reproduction of data from the MD, thereby providingcontinuous playback of the contents of the data. Specifically, dataremain read out from the shock-proof memory and playback of the contentsof the data continues even for a time during which the pickup jumps froma sector to a next sector while kicking across recording tracks on theMD and waiting for disc rotation to meet the next sector.

[0005] During the recording mode of operation of the MD player, a pickupsequentially accesses sectors on the MD and records data thereon. In theMD player, compressed data to be recorded are temporarily stored in theshock-proof memory. The compressed data are intermittently read out fromthe memory before being fed to the pickup and being recorded on the MDthereby. Thus, during the recording mode of operation of the MD player,the feed of data to the pickup is intermittently executed. The absenceof data feed to the pickup is synchronized with jump of the pickup froma sector to a next sector. Accordingly, during the absence of data feed,the pickup jumps from a sector to a next sector while kicking acrossrecording tracks on the MD and waiting for disc rotation to meet thenext sector.

[0006] Optical discs contain a DVD (Digital Video Disc or DigitalVersatile Disc). DVD players include shock-proof memories similar infunction to those in the MD players. Typical shock-proof memories in theDVD players have a capacity of 16 MB which corresponds to a playbacktime of about 2 seconds. Advanced shock-proof memories in the DVDplayers have a capacity of more than 16 MB which corresponds to aplayback time of longer than 2 seconds.

[0007] Optical discs are of a read only type (a playback only type), arecordable type (a write once type), and a rewritable type. A CD(Compact Disc), a VCD (Video CD), and a DVD are optical discs of theread only type. A CD-R and a DVD-R are optical discs of the recordabletype. A CD-RW, a DVD-RAM, and a DVD-RW are optical discs of therewritable type.

[0008] Optical discs of the rewritable type have thin recording filmswhich are reversibly changed between two or more different states inaccordance with conditions of laser beams applied thereto. Rewritableoptical discs include magneto-optical discs and phase change discs.

[0009] In the case of a phase change optical disc, while a recordingfilm is scanned by a laser beam, the recording film is reversiblychanged between an amorphous state and a crystalline state by changingconditions of the laser beam in response to a signal to be recorded.Thus, the signal is recorded on the recording film as a pattern ofamorphous portions and crystalline portions of the recording film. Thesignal is reproduced from the phase change optical disc as follows. Thesurface of an amorphous portion of the disc and the surface of acrystalline portion thereof are different in reflectivity with respectto a laser beam. While the phase change optical disc is scanned by alaser beam, a change in reflectivity of the disc surface with respect tothe laser beam is optically detected so that the signal is reproducedfrom the disc.

[0010] The phase change optical disc is similar to a read only opticaldisc and a recordable optical disc in the point that signal reproductionis implemented by detecting a change in the disc surface reflectivitywith respect to a laser beam. Signal overwriting on the phase changeoptical disc can be performed by use of only one laser beam when thelaser power is modulated between an erasing level Pe and a recordinglevel Pw. Therefore, the structure of a drive device for the phasechange optical disc can be simple.

[0011] It is conceivable to use a PWM (pulse width modulation) system torecord a signal on a rewritable optical disc at a high density.According to the PWM system, the positions of the front and rear edgesof every recording mark on the disc correspond to “1” in a digitalsignal.

[0012] In the PWM system, the width of every recording mark representsinformation. Thus, a desirable shape of the recording mark is free fromdistortion. Specifically, it is desirable that the shapes of the frontand rear halves of the recording mark are symmetrical with each other.During the PWM-based recording of a signal on the disc, the disc isexposed to a laser beam while being rotated and moved relative thereto.In addition, the intensity of the laser beam is changed between strongand weak levels in response to the signal to be recorded. Recordingmarks are formed on portions of the disc which are exposed to thestronger laser beam. Regarding every recording mark, the heataccumulation effect causes the stronger-beam-application ending point onthe disc to be higher in temperature than the stronger-beam-applicationstarting point on the disc. As a result, the rear end of the recordingmark is wider than the front end thereof. Thus, the shape of therecording mark is distorted.

[0013] Japanese published unexamined patent application 3-185628discloses a method of reducing distortion in the shape of a recordingmark. The method in Japanese application 3-185628 is an overwritingmethod in which one recording mark is formed by the application of atrain of short pulses (narrow pulses) of a laser beam to a disc.

[0014] Japanese published unexamined patent application 6-12674discloses a method of correcting the waveform of a train of electricpulses fed to a laser source. According to the method in Japaneseapplication 6-12674, an input signal repetitively changes between a highlevel state and a low level state. The input signal being continuouslyin the high level state corresponds to one recording mark. The inputsignal being continuously in the high level state is converted into atrain of electric short pulses (electric narrow pulses). The first pulsein the train is wider than the second and later pulses therein. Thenumber of the pulses in the train is determined by a desired length ofthe recording mark. The electric pulse train is fed to the laser source.The electric pulse train is converted by the laser source into acorresponding train of short pulses (narrow pulses) of a laser beam. Thelaser beam pulse train is applied to a disc. One recording mark isformed on the disc in response to the laser beam pulse train. Since thefirst pulse in the train is relatively wide, the temperature of thebeam-train-application starting point on the disc quickly rises. On theother hand, since the second and later pulses in the train arerelatively narrow, the temperature of the beam-train-application endingpoint on the disc is prevented from excessively rising. Therefore, it ispossible to compensate for the heat accumulation effect which wouldcause distortion of the recording mark.

[0015] The shape-distortion reducing technique in Japanese application6-12674 is less effective as the linear velocity related to the scanningof a disc increases. In the method of Japanese application 6-12674, atrain of short pulses (narrow pulses) of a laser beam is applied to therecording film of a disc to form a recording mark thereon. The pulsativelaser beam results in decreased energy applied to the recording film ofthe disc. Accordingly, a required instantaneous power of the laser beamis relatively high. In addition, a required instantaneous power of thelaser beam rises as the linear velocity related to the scanning of thedisc increases. A high-power laser source is expensive.

[0016] In the method of Japanese application 6-12674, the input signalbeing continuously in the high level state is converted into a train ofelectric short pulses. It is necessary to use a clock signal in theconversion of the high-level input signal into the electric pulse train.The period of the clock signal is equal to the period of the inputsignal which is divided by a given integer. As the frequency of theinput signal rises, the required frequency of the clock signalincreases. An excessively high frequency of the clock signal causesdifficulty in circuit designing. Modulation of the laser power at ahigher frequency causes greater distortion in the waveform of the laserbeam.

[0017] In a CAV (constant angular velocity) disc drive system, a disc isrotated at a constant angular speed. In this case, the linear velocityrelated to the scanning of an outer portion of the disc is higher thanthat of an inner portion of the disc. According to a proposed method,the length of a recording mark on an inner portion of a disc and thelength of that on an outer portion of the disc are set the same toincrease the recording density. In the proposed method, the recordingfrequency at a position on the disc increases as the position is closerto the outer edge of the disc.

[0018] In a CLV (constant linear velocity) disc drive system, a disc isrotated at a constant linear speed. A conceivable CLV recordingapparatus is able to record signals on discs of different types. Theconceivable CLV recording apparatus is required to change the linearvelocity and the recording frequency depending on the disc type.

[0019] Optimal recording conditions of a disc having a high recordingdensity vary from disc to disc. In addition, the optimal recordingconditions depend on the number of times of signal recording on thedisc, the ambient temperature, and other factors. According to aconceivable method of detecting optimal recording conditions of a disc,signal recording on the disc is interrupted, and a recording head ismoved to a test area of the disc. Then, a test signal is recorded on thetest area, and the test signal is reproduced therefrom. The quality ofthe reproduced test signal is measured. Optimal recording conditions ofthe disc are detected on the basis of the measurement results. After theoptimal recording conditions are detected, the recording of a maininformation signal on the disc is started. The recording of the maininformation signal is implemented under the optimal recordingconditions. In the conceivable method, the detection of optimalrecording conditions takes a long time. Thus, there is a long wait untilthe recording of the main information signal on the disc is started.

[0020] The power of a laser beam depends on the ambient temperature andthe aging of a laser source. To maintain accurate signal recording on adisc, it is necessary to compensate for such a variation in the power ofthe laser beam. In a conceivable method, signal recording on the disc isinterrupted, and the power of a laser beam is measured. Optimal driveconditions of a laser source are decided on the basis of the measurementresults. In the conceivable method, the decision as to optimal driveconditions of the laser source takes a long time.

[0021] A prior-art method of detecting optimal recording conditions of aCD-R has a step of measuring the asymmetry of a reproduced signal. ADVD-R, a DVD-RW, other organic-dye recordable optical discs, other phasechange rewritable optical discs, and other recordable and rewritableoptical discs having high recording densities are made from variousselections of materials in various fabrication methods. Therefore, ifthe prior-art method is applied to such a high-recording-density disc,the results of the detection of optimal recording conditions areunreliable.

[0022] A phase change optical disc has the following problem. As a samesignal is repetitively recorded on a same position on the disc at a sametiming, the jitter-related quality of a signal reproduced therefromdeteriorates.

SUMMARY OF THE INVENTION

[0023] It is a first object of this invention to provide an improvedapparatus for recording and reproducing information on and from anoptical disc.

[0024] It is a second object of this invention to provide an improvedmethod of recording and reproducing information on and from an opticaldisc.

[0025] It is a third object of this invention to provide an improvedoptical disc.

[0026] A first aspect of this invention provides an apparatus forrecording and reproducing an information signal on and from an opticaldisc. The apparatus comprises a memory; means for writing theinformation signal into the memory; means for reading out theinformation signal from the memory; an optical head for generating alaser beam in response to the readout information signal, and applyingthe laser beam to the optical disc to record the readout informationsignal on the optical disc; means for recording a test signal on aposition of the optical disc near a recording position thereof via theoptical head during the writing of the information signal into thememory; means for reproducing the test signal from the optical disc;means for evaluating the reproduced test signal to generate anevaluation result; and means for optimizing an intensity of the laserbeam in response to the evaluation result.

[0027] A second aspect of this invention provides an apparatus forrecording and reproducing an information signal on and from an opticaldisc. The apparatus comprises a memory; means for writing theinformation signal into the memory; means for reading out theinformation signal from the memory; an optical head for generating alaser beam in response to the readout information signal, and applyingthe laser beam to the optical disc to record the readout informationsignal on the optical disc; means for changing a power of the laser beamamong a plurality of different levels; means for measuring the laserbeam to generate measurement result values during the change of thepower of the laser beam among the plurality of the different levels; andmeans for optimizing an intensity of the laser beam in response to themeasurement result values.

[0028] A third aspect of this invention is based on the first aspectthereof, and provides an apparatus wherein the test signal comprises atest pattern signal, and the recording means comprises means forrecording the test pattern signal on the optical disc via the opticalhead while changing an intensity of the laser beam among a plurality ofdifferent levels for a testing purpose, and wherein the reproducingmeans comprises means for reproducing the test pattern signal from theoptical disc, and the evaluating means comprises means for evaluating atleast one of asymmetry and jitter of the reproduced test pattern signalto generate the evaluation result.

[0029] A fourth aspect of this invention is based on the second aspectthereof, and provides an apparatus further comprising means forrepetitively measuring the laser beam to repetitively generate ameasurement result value, means for calculating a difference between acurrent measurement result value and an immediately precedingmeasurement result value, and means for enabling the optimizing means tooptimize the intensity of the laser beam when the calculated differenceis equal to or greater than a predetermined value.

[0030] A fifth aspect of this invention is based on the first aspectthereof, and provides an apparatus further comprising means forrepetitively measuring a temperature to repetitively generate a measuredtemperature value, means for calculating a difference between a currentmeasured temperature value and an immediately preceding measuredtemperature value, and means for enabling the optimizing means tooptimize the intensity of the laser beam when the calculated differenceis equal to or greater than a predetermined value.

[0031] A sixth aspect of this invention is based on the first aspectthereof, and provides an apparatus further comprising means formeasuring a lapse of time since a moment of the last optimization of theintensity of the laser beam, and for deciding whether or not themeasured lapse of time exceeds a predetermined time to generate adecision result, and means for optimizing the intensity of the laserbeam in response to the decision result.

[0032] A seventh aspect of this invention is based on the first aspectthereof, and provides an apparatus further comprising means formeasuring a distance between a current recording position and a nextrecording position on the optical disc, and deciding whether or not themeasured distance exceeds a predetermined distance to generate adecision result, and means for optimizing the intensity of the laserbeam in response to the decision result.

[0033] An eighth aspect of this invention provides a method of recordingand reproducing an information signal on and from an optical disc. Themethod comprises the steps of writing an information signal into amemory; reading out the information signal from the memory; generating alaser beam in response to the readout information signal, and applyingthe laser beam to the optical disc to record the readout informationsignal on the optical disc; recording a test signal on a position of theoptical disc near a recording position thereof via the optical headduring the writing of the information signal into the memory;reproducing the test signal from the optical disc; evaluating thereproduced test signal to generate an evaluation result; and optimizingan intensity of the laser beam in response to the evaluation result.

[0034] A ninth aspect of this invention provides an optical disc havingan area storing information of an intensity of a laser beam which hasbeen optimized by the apparatus of the first aspect of this invention.

[0035] A tenth aspect of this invention provides n apparatus forrecording and reproducing an information signal on and from an opticaldisc. The apparatus comprises a memory; means for writing theinformation signal into the memory; means for reading out theinformation signal from the memory; an optical head for generating alaser beam in response to the readout information signal, and applyingthe laser beam to the optical disc to record the readout informationsignal on the optical disc; means for recording a test signal on aposition of the optical disc near a recording position thereof via theoptical head during the writing of the information signal into thememory; means for reproducing the test signal from the optical disc;first optimizing means for measuring asymmetry of the reproduced testsignal, and optimizing an intensity of the laser beam in response to themeasured asymmetry; second optimizing means for measuring jitter of thereproduced test signal, and optimizing the intensity of the laser beamin response to the measured jitter; third optimizing means for measuringthe laser beam to generate a measurement result, and optimizing theintensity of the laser beam in response to the measurement result; meansfor detecting a type of the optical disc; and means for selecting atleast one of the first, second, and third optimizing means in responseto the detected type, and enabling the selected one of the first,second, and third optimizing means.

[0036] An eleventh aspect of this invention is based on the tenth aspectthereof, and provides an apparatus wherein the type detecting meanscomprises means for deciding whether the type of the optical disc is anorganic-dye type or a phase change type to generate a type decisionresult, and the selecting means comprises means for selecting at leastone of the first, second, and third optimizing means in response to thetype decision result, and enabling the selected one of the first,second, and third optimizing means.

[0037] A twelfth aspect of this invention is based on the tenth aspectthereof, and provides an apparatus wherein the type detecting meanscomprises means for reproducing disc information from the optical disc,and means for deriving a disc maker from the reproduced discinformation, and wherein the selecting means comprises means forselecting at least one of the first, second, and third optimizing meansin response to the disc maker, and enabling the selected one of thefirst, second, and third optimizing means.

[0038] A thirteenth aspect of this invention is based on the tenthaspect thereof, and provides an apparatus wherein the type detectingmeans comprises means for reproducing disc information from the opticaldisc, and means for deriving a disc article number from the reproduceddisc information, and wherein the selecting means comprises means forselecting at least one of the first, second, and third optimizing meansin response to the disc article number, and enabling the selected one ofthe first, second, and third optimizing means.

[0039] A fourteenth aspect of this invention is based on the tenthaspect thereof, and provides an apparatus wherein the type detectingmeans comprises means for reproducing disc information from the opticaldisc, and means for deriving a disc production lot number from thereproduced disc information, and wherein the selecting means comprisesmeans for selecting at least one of the first, second, and thirdoptimizing means in response to the disc production lot number, andenabling the selected one of the first, second, and third optimizingmeans.

[0040] A fifteenth aspect of this invention provides an apparatus forrecording and reproducing an information signal on and from an opticaldisc. The apparatus comprises a memory; means for writing theinformation signal into the memory; means for reading out theinformation signal from the memory; an optical head for generating alaser beam in response to the readout information signal, and applyingthe laser beam to the optical disc to record the readout informationsignal on the optical disc; means for repetitively recording a testsignal on a place on the optical disc via the optical head, the placebeing near a recording position of the optical disc which is subjectedto signal recording next; means for reproducing the test signal from theoptical disc; means for evaluating the reproduced test signal togenerate an evaluation result; means for optimizing an intensity of thelaser beam in response to the evaluation result; and means for changingthe test signal on a recording-by-recording basis.

[0041] A sixteenth aspect of this invention is based on the fifteenthaspect thereof, and provides an apparatus wherein the changing meanscomprises means for generating a random signal providing a randomtiming, and means for shifting the test signal in response to the randomtiming to change the test signal on the recording-by-recording basis.

[0042] A seventeenth aspect of this invention is based on the fifteenthaspect thereof, and provides an apparatus wherein the changing meanscomprises means for time-positionally exchanging signal segments of thetest signal to change the test signal on the recording-by-recordingbasis.

[0043] An eighteenth aspect of this invention provides an apparatus forrecording and reproducing an information signal on and from an opticaldisc. The apparatus comprises means for generating a laser beam inresponse to a first time segment of the information signal, and applyingthe laser beam to a first place on the optical disc to record the firsttime segment of the information signal on the first place on the opticaldisc; means for generating a laser beam in response to a test signal,and applying the laser beam to a second place on the optical disc torecord the test signal on the second place on the optical disc whilechanging the laser beam among a plurality of conditions different fromeach other, the second place immediately following the first place;means for reproducing the test signal from the optical disc; means forevaluating the reproduced test signal to generate evaluation resultscorresponding to the respective different conditions of the laser beam;means for deciding a best of the evaluation results; and means forgenerating a laser beam in one of the different conditions whichcorresponds to the best evaluation result and in response to a secondtime segment of the information signal, and applying the laser beam tothe second place on the optical disc to write the second time segment ofthe information signal over the test signal on the second place on theoptical disc, the second time segment immediately following the firsttime segment.

[0044] A nineteenth aspect of this invention is based on the eighteenthaspect thereof, and provides an apparatus wherein the differentconditions of the laser beam comprise different conditions of pulses inpulse trains of the laser beam.

[0045] A twentieth aspect of this invention provides an apparatus forrecording and reproducing an information signal on and from an opticaldisc. The apparatus comprises a memory; means for writing theinformation signal into the memory; means for reading out theinformation signal from the memory; an optical head for generating alaser beam in response to the readout information signal, and applyingthe laser beam to the optical disc to record the readout informationsignal on the optical disc; means for recording a test signal on theoptical disc via the optical head while changing the laser beam among aplurality of conditions different from each other for a testing purposeduring the writing of the information signal into the memory; means forreproducing the test signal from the optical disc; means for evaluatingthe reproduced test signal to generate evaluation results correspondingto the respective different conditions of the laser beam; means fordeciding a best of the evaluation results; and means for controlling thelaser beam into one of the different conditions which corresponds to thebest evaluation result.

[0046] A twenty-first aspect of this invention is based on the twentiethaspect thereof, and provides an apparatus wherein the differentconditions of the laser beam comprise different conditions of pulses inpulse trains of the laser beam.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047]FIG. 1 is a time-domain diagram of a waveform of an input signal,and recording waveforms of a laser beam.

[0048]FIG. 2 is a sectional view of a portion of an optical disc.

[0049]FIG. 3 is a time-domain diagram of a waveform of an input signal,and recording waveforms of a laser beam.

[0050]FIG. 4 is a diagram of the relation between a disc-scanning linearvelocity and a phase margin.

[0051]FIG. 5 is a diagram of the relation among the disc-scanning linearvelocity, the phase margin, and a temperature.

[0052]FIG. 6 is a diagram of the relation between the disc-scanninglinear velocity and a recording power.

[0053]FIG. 7 is a diagram of a recording waveform of a laser beam.

[0054]FIG. 8 is a diagram of a recording waveform of a laser beam.

[0055]FIG. 9 is a block diagram of an information-signal recording andreproducing apparatus according to a first embodiment of this invention.

[0056]FIG. 10 is a diagrammatic plan view of an optical disc.

[0057]FIG. 11 is a block diagram of an amplifier unit in FIG. 9.

[0058]FIG. 12 is a diagram of addresses on an optical disc, and datarecorded on the disc.

[0059]FIG. 13 is a time-domain diagram of the degree of the occupancy ofa memory in FIG. 9.

[0060]FIG. 14 is a flowchart of a segment of a program for a systemcontroller in FIG. 9.

[0061]FIG. 15 is a flowchart of a block in FIG. 14.

[0062]FIG. 16 is a block diagram of an asymmetry detection circuit inFIG. 11.

[0063]FIG. 17 is a flowchart of a block in a program segment in a secondembodiment of this invention.

[0064]FIG. 18 is a flowchart of a block in a program segment in a thirdembodiment of this invention.

[0065]FIG. 19 is a flowchart of a block in a program segment in a fourthembodiment of this invention.

[0066]FIG. 20 is a flowchart of a block in a program segment in a fifthembodiment of this invention.

[0067]FIG. 21 is a flowchart of a block in a program segment in a sixthembodiment of this invention.

[0068]FIG. 22 is a flowchart of a block in a program segment in aseventh embodiment of this invention.

[0069]FIG. 23 is a flowchart of a block in a program segment in afifteenth embodiment of this invention.

[0070]FIG. 24 is a diagram of a recording waveform of a laser beam.

[0071]FIG. 25 is a diagram of a recording waveform of a laser beam.

[0072]FIG. 26 is a flowchart of a program segment in a twenty-seventhembodiment of this invention.

[0073]FIG. 27 is a flowchart of a program segment in a twenty-ninthembodiment of this invention.

[0074]FIG. 28 is a time-domain diagram of a wobble signal, a recordingclock signal, an LPP signal, and a timing signal.

[0075]FIG. 29 is a block diagram of a waveform correction circuit inFIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

[0076] A first embodiment of this invention is designed to correct arecording laser beam into an optimal waveform in accordance with thetype of an optical disc and a variation in the linear velocity relatedto the scanning of the disc.

[0077] As shown in FIG. 1, an input signal (for example, an 8-16modulation-resultant signal) repetitively changes between a high levelstate and a low level state. In the case where the linear velocityrelated to the scanning of the disc is lower than a preset velocity, alaser beam is modulated into a recording waveform WAO having trains ofshort pulses (narrow pulses). The power of the laser beam changesbetween an erasing level Pe and a recording level Pw. Each laser-beampulse train in the recording waveform WAO corresponds to the inputsignal being continuously in the high level state. The first pulse inthe train is wider than the second and later pulses therein. The numberof the pulses in the train increases as the time interval for which theinput signal is continuously in the high level state increases.

[0078] In the case where the linear velocity related to the scanning ofthe disc is equal to or higher than the preset velocity, the laser beamis modulated into a recording waveform WBO having wide pulses as shownin FIG. 1. The power of the laser beam changes between an erasing levelPe and a recording level Pw. Each laser-beam pulse in the recordingwaveform WBO corresponds to the input signal being continuously in thehigh level state. The duration of the laser-beam pulse is slightlyshorter than the corresponding time interval for which the input signalis continuously in the high level state.

[0079] Experiments were performed to determine the relation between thelinear velocity related to the scanning of a phase change optical discand the waveform distortion of a signal reproduced from the disc. Duringthe experiments, signal recording on and signal reproduction from thedisc were implemented while the linear velocity and the recordingwaveform were changed.

[0080] As shown in FIG. 2, the phase change optical disc used in theexperiments included a substrate 1 made of polycarbonate. The disc had adiameter of 120 mm. The disc was formed with a signal recording track. Adielectric film 3, a recording film 2, a dielectric film 4, and areflecting layer 5 were sequentially laminated on the substrate 1 inthat order. The recording film 2 was made of GeSbTe. The recording film2 had a thickness of 20 nm. The dielectric films 3 and 4 were made ofZnS. The dielectric film 3 had a thickness of 150 nm. The dielectricfilm 4 had a thickness of 15 nm. The reflecting film 5 was made of Au.The reflecting film 5 had a thickness of 50 nm.

[0081] After the whole surface of the recording film 2 of the disc wascrystallized (that is, after a signal was completely erased from thewhole surface of the recording film 2 of the disc), the disc was scannedby a laser beam responsive to an input signal. Specifically, while thedisc was rotated, the laser beam having a recording power level wasintermittently applied to the surface of the recording film 2 inresponse to the input signal. Portions of the surface of the recordingfilm 2 which were exposed to the recording-power-level laser beamchanged to an amorphous state. Thus, the input signal was recorded onthe recording film 2 as recording marks formed by the respectiveamorphous portions of the surface of the recording film 2. The linearvelocity related to the scanning of the disc was changed among 1.5 m/s,3 m/s, 6 m/s, and 9 m/s. The input signal was an 8-16modulation-resultant signal. The laser beam was emitted from asemiconductor laser. The input signal was recorded on the disc by usinga laser-beam recording waveform WA based on the recording waveform WAO(see FIG. 1). In addition, the input signal was recorded on the disc byusing a laser-beam recording waveform WB corresponding to the recordingwaveform WBO (see FIG. 1).

[0082] As shown in FIG. 3, the 8-16 modulation-resultant signal (theinput signal) repetitively changed between a high level state and a lowlevel state. A clock signal (a bit clock signal) related to the 8-16modulation-resultant signal had a period T. The period T is alsoindicated as T. As shown in FIG. 3, the laser-beam recording waveform WAwas generated in response to the 8-16 modulation-resultant signal (theinput signal). According to the laser-beam recording waveform WA, thepower (or the intensity) of the laser beam changed between an erasinglevel Pb and a recording level Pp.

[0083] It should be noted that the erasing level Pb and the recordinglevel Pp may be variable. The laser-beam recording waveform WA hadtrains of short pulses (narrow pulses). Each laser-beam pulse train inthe recording waveform WA corresponded to the 8-16 modulation-resultantsignal being continuously in the high level state. The moment of theoccurrence of the leading edge of the first pulse in the train followsthe moment of the occurrence of the rising edge in the 8-16modulation-resultant signal by a time interval Ta set to T. The firstpulse in the train had a width or duration Tb set to 1.5T. The secondand later pulses in the train had a width or duration Td set to 0.5T. Inthe train, the pulses were spaced at intervals Tc set to 0.5T. It shouldbe noted that the time intervals Ta, Th, Tc, and Td may be variable. Aclock signal used to generate the laser-beam recording waveform WA had afrequency equal to twice the frequency of the clock signal related tothe 8-16 modulation-resultant signal.

[0084] As shown in FIG. 3, the laser-beam recording waveform WB wasgenerated in response to the 8-16 modulation-resultant signal (the inputsignal). According to the laser-beam recording waveform WB, the power(or the intensity) of the laser beam changed between an erasing level Pband a recording level Pp. The laser-beam recording waveform WB had widepulses. Each laser-beam pulse in the recording waveform WB correspondedto the 8-16 modulation-resultant signal being continuously in the highlevel state. The duration of the laser-beam pulse is shorter than thecorresponding time interval for which the input signal is continuouslyin the high level state by a value set to T. The moment of theoccurrence of the leading edge of the laser-beam pulse follows themoment of the occurrence of the rising edge in the 8-16modulation-resultant signal by a time interval set to T.

[0085] The frequency of the clock signal related to the 8-16modulation-resultant signal was varied in response to the disc-scanninglinear velocity so that the lengths of recording marks on the discremained constant independent of the disc-scanning linear velocity.Specifically, the clock frequency was 4.3 MHz when the linear velocitywas 1.5 m/s. The clock frequency was 8.6 MHz when the linear velocitywas 3 m/s. The clock frequency was 17.2 MHz when the linear velocity was6 m/s. The clock frequency was 25.8 MHz when the linear velocity was 9m/s.

[0086] After the signal was recorded on the disc, the signal wasreproduced therefrom. The waveform distortion of the reproduced signalwas quantitatively evaluated. Specifically, the reproduced signal wasconverted into a binary signal (a two-level signal). The binary signalwas inputted into a time interval analyzer so that the jitter amount ofthe binary signal was detected as a phase margin. The errors of thepositions of the front and rear edges of recording marks decreased andhence the distortions of the recording marks decreased as the phasemargin increased.

[0087] During the experiments, the phase margin was measured for each ofoptical discs of several types. FIG. 4 shows the experimentally obtainedrelation between the variation in the phase margin and the linearvelocity related to the scanning of the discs. The recording waveform WAwas used when the linear velocity was 1.5 m/s, 3.0 m/s, and 6.0 m/s. Therecording waveform WB was used when the linear velocity was 9.0 m/s.With reference to FIG. 4, the phase margin increased as the linearvelocity increased. As shown in FIG. 5, the relation between the phasemargin and the disc-scanning linear velocity depended on the ambienttemperature of the disc. Specifically, the phase margin increased as theambient temperature of the disc rose. As shown in FIG. 6, the recordingpower level Pp of the laser beam on the disc and having the waveform WAwas increased in accordance with an increase in the disc-scanning linearvelocity. The erasing power level Pb of the laser beam on the discremained constant regardless of the type of the recording waveform andindependent of the disc-scanning linear velocity.

[0088] As is clear from FIG. 4, the recording waveform WA is good inthat the phase margin increases as the disc-scanning velocity increases.In the case of the recording waveform WA, the phase margin varies fromdisc to disc. It is revealed in FIG. 5 that the phase margin depends onthe ambient disc temperature. The cause of the dependency of the phasemargin on the ambient disc temperature is as follows. Signal overwritingon the disc is governed by the temperature to which the recording filmof the disc is heated. The temperature to which the recording film ofthe disc is heated deviates from the optimal value due to a fluctuationin the disc-scanning linear velocity, a variation in the ambient disctemperature, and a disc-by-disc variation in the disc conditions. Asshown in FIG. 6, the recording power level Pp of the laser beam is setrelatively great since the recording waveform WA applies pulsativeenergy to the recording film of the disc. Thus, a high-powersemiconductor laser is used for drive of the disc at a high linearvelocity.

[0089]FIG. 7 shows a laser-beam recording waveform WC which may replacethe laser-beam recording waveform WA (see FIG. 3). The recordingwaveform WC is similar to the recording waveform WA except for thefollowing points. In the recording waveform WC of FIG. 7, during alimited time interval immediately preceding each pulse train, the powerof a laser beam is lower than an erasing level Pb. Also, during alimited time interval immediately following each pulse train, the powerof the laser beam is lower than the erasing level Pb. In the case whereintervals between recording marks are relatively narrow, there occursheat interference such that heat of forming a recording mark diffusesrearward into a disc portion to be exposed to a recording-power laserbeam next and hence a next recording mark has a greater size. Therecording waveform WC reduces the effect of heat interference. Thus, therecording waveform WC is advantageous in increasing the phase margin. Inthe case where the limited time interval for which the power of thelaser beam is lower than the erasing level Pb is excessively long, therecording film of the disc does not reach the crystallizationtemperature and hence the recorded signal fails to be erased. To preventsuch a problem, it is preferable that the limited time interval “τ” forwhich the power of the laser beam is lower than the erasing level Pb hasthe following relation with the wavelength “λ” of the laser beam and therelative speed “V” between the laser beam spot and the disc.

τ≦λ/V  (1)

[0090] As long as the relation (1) is satisfied, the recording film in adisc portion assigned to a recording mark is surely heated to thecrystallization temperature by application of the recording-power laserbeam thereto and also application of the erasing-power laser beam to aprevious disc portion.

[0091] The laser-beam recording waveform WC may be modified as follows.According to a first modification of the laser-beam recording waveformWC, only during the limited time interval immediately preceding eachpulse train, the power of a laser beam is lower than the erasing levelPb. According to a second modification of the laser-beam recordingwaveform WC, only during the limited time interval immediately followingeach pulse train, the power of the laser beam is lower than the erasinglevel Pb.

[0092] In the laser-beam recording waveform WC, the low power level ofthe laser beam which occurs during every limited time interval may beequal to a reproducing power level or a null power level. In this case,the structure of the disc drive can be simple.

[0093] The laser-beam recording waveform WB (see FIG. 3) may be modifiedas follows. According to a first modification of the laser-beamrecording waveform WB, during a limited time interval immediatelypreceding each pulse, the power of a laser beam is lower than theerasing level Pb. Also, during a limited time interval immediatelyfollowing each pulse, the power of the laser beam is lower than theerasing level Pb. According to a second modification of the laser-beamrecording waveform WB, only during the limited time interval immediatelypreceding each pulse, the power of the laser beam is lower than theerasing level Pb. According to a third modification of the laser-beamrecording waveform WB, only during the limited time interval immediatelyfollowing each pulse, the power of the laser beam is lower than theerasing level Pb.

[0094]FIG. 8 shows a laser-beam recording waveform WD which may replacethe laser-beam recording waveform WC (see FIG. 7) or the laser-beamrecording waveform WA (see FIG. 3). The recording waveform WD is similarto the recording waveform WC except for the following point. Accordingto the recording waveform WD of FIG. 8, in each pulse train, the powerof a laser beam changes between a recording level Pp and a reproducinglevel (or a null level). The recording waveform WD causes every positionin a recording mark to be quickly cooled after being melt. Thus, it ispossible to stably form a recording mark. In addition, the recordingwaveform WD is advantageous in increasing the phase margin.

[0095]FIG. 9 shows an information-signal recording and reproducingapparatus according to the first embodiment of this invention. Theapparatus of FIG. 9 operates on a rewritable optical disc such as aDVD-RW. The DVD-RW is driven on a CLV basis. The DVD-RW has sectorsextending along a spiral recording track. One sector has 16 bytesassigned to an address, and 2,048 bytes assigned to data. Regarding theDVD-RW, one ECC block having 16 sectors is a minimum unit of errorcorrection. Also, one ECC block is a minimum unit for signalreproduction from and signal recording on the DVD-RW.

[0096] As shown in FIG. 10, the DVD-RW is divided into an inner area EAand an outer area EB. When the inner edge of the area EA is scanned by alaser beam, the period of rotation of the disc is equal to about 40msec. When the outer edge of the area EB is scanned by the laser beam,the period of rotation of the disc is equal to about 80 msec.

[0097] The DVD-RW in FIG. 10 may be designed as follows. In the innerarea EA, 2 ECC blocks each having 16 sectors compose a general 1-unitcorresponding block (a general reproduction and recording unit). In theouter area EB, 4 ECC blocks compose a general 1-unit corresponding block(a general reproduction and recording unit).

[0098] The apparatus of FIG. 9 includes a key input unit 10, a systemcontroller 12, a signal processor 14, a servo processor 16, a driver 18,a spindle motor 20, an optical head (optical pickup) 24, an amplifierunit 26, a memory 28, an audio-video encoding and decoding unit 30, amemory 32, an input/output terminal 34, and a temperature sensor 36.

[0099] The spindle motor 20 acts to rotate a rewritable optical disc 22such as a DVD-RW. While the spindle motor 20 rotates the optical disc22, the optical head 24 writes and reads information thereon andtherefrom. The spindle motor 20 is connected to the driver 18. Theoptical head 24 is connected to the amplifier unit 26 and the driver 18.The amplifier unit 26 is connected to the servo processor 16 and thesignal processor 14. The driver 18 is connected to the servo processor16. The signal processor 14 is connected to the memory 28 and theaudio-video encoding and decoding unit 30. The audio-video encoding anddecoding unit 30 is connected to the memory 32 and the input/outputterminal 34. The system controller 12 is connected to the key input unit10, the signal processor 14, the servo processor 16, the amplifier unit26, and the audio-video encoding and decoding unit 30. The temperaturesensor 36 is located near the optical disc 22 placed in position withinthe apparatus. The temperature sensor 36 detects an ambient temperatureof the optical disc 22. The temperature sensor 36 is connected to theamplifier unit 26.

[0100] The spindle motor 20 is driven and controlled by the driver 18.The spindle motor 20 rotates the optical disc 22. The spindle motor 20is provided with an FG generator and a rotational position sensor (anangular position sensor). The rotational position sensor includes, forexample, a Hall element. The FG generator outputs an FG signal (arotational speed signal). The Hall element outputs a rotational positionsignal. The FG signal and the rotational position signal are fed back tothe driver 18.

[0101] The optical head 24 faces the optical disc 22 placed in positionwithin the apparatus. A feed motor (not shown) moves the optical head 24radially with respect to the optical disc 22. The feed motor is drivenby the driver 18. The optical head 24 includes a semiconductor laser, acollimator lens, and an objective lens. The semiconductor laser acts asa source for emitting a light beam (a laser beam). The emitted laserbeam is focused into a laser spot on the optical disc 22 by thecollimator lens and the objective lens. The optical head 24 includes a2-axis actuator for driving the objective lens to implement focusing andtracking of the laser spot with respect to the optical disc 22. Thesemiconductor laser is driven by a laser drive circuit in the amplifierunit 26. In the case where an information signal such as an audio signalor an audio-video signal is recorded, the information signal issubjected to waveform correction by a waveform correction circuit in theamplifier unit 26 before being fed to the laser drive circuit. The2-axis actuator is driven by the driver 18.

[0102] The key input unit 10 includes a plurality of keys which can beoperated by a user. The key input unit 10 generates command signals inaccordance with its operation by the user. The command signals aretransmitted from the key input unit 10 to the system controller 12. Thecommand signals include a command signal for starting a recording modeof operation of the apparatus, and a command signal for starting aplayback mode of operation of the apparatus. The key input unit 10generates control data in accordance with its operation by the user. Thecontrol data are transmitted from the key input unit 10 to the systemcontroller 12.

[0103] The system controller 12 includes, for example, a microcomputeror a similar device which operates in accordance with a program storedin its internal ROM. The system controller 12 controls the signalprocessor 14, the servo processor 16, the amplifier unit 26, and theaudio-video encoding and decoding unit 30 in response to the commandsignals fed from the key input unit 10.

[0104] Control data can be fed to the system controller 12 via an inputterminal (not shown). The control data fed to the system controller 12via the input terminal, and the control data fed to the systemcontroller 12 from the key input unit 10 include a signal for adjustingthe resolution of pictures represented by contents information to berecorded, a signal for separating quickly-moving scenes such as carracing scenes represented by contents information, and a signal forgiving priority to a recording time. The system controller 12 changes anactual recording time in accordance with the control data. The change ofthe actual recording time is implemented by changing, for example, adata compression rate used by the audio-video encoding and decoding unit30. The system controller 12 enables the setting of the actual recordingtime to be selected by the user.

[0105] When the apparatus is required to start to operate in theplayback mode, the key input unit 10 is actuated to generate theplayback start command signal. The playback start command signal istransmitted from the key input unit 10 to the system controller 12. Thesystem controller 12 controls the servo processor 16 and the amplifierunit 26 in response to the playback start command signal, therebystarting the playback mode of operation of the apparatus. The control ofthe servo processor 16 includes steps of controlling the driver 18.Firstly, the system controller 12 starts rotation of the optical disc 22and application of a laser spot thereon through the control of thedriver 18. The optical head 24 is controlled by the driver 18, therebyreading out address information from the optical disc 22. The readoutaddress information is transmitted from the optical head 24 to thesystem controller 12 via the amplifier unit 26. The system controller 12finds or decides a target sector (a target track portion) to be playedback by referring to the address information. The system controller 12controls the optical head 24 via the servo processor 16, the driver 18,and the feed motor, thereby moving the optical head 24 radially withrespect to the optical disc 22 and hence moving the laser spot to thetarget sector on the optical disc 22. When the movement of the laserspot to the target sector is completed, the system controller 12operates to start the reproduction of a signal from the target sector onthe optical disc 22. In this way, the playback mode of operation of theapparatus is started. During the playback mode of operation of theapparatus, the target sector is repetitively changed from one toanother.

[0106] During the playback mode of operation of the apparatus, theoptical head 24 scans the optical disc 22 and generates a reproduced RFsignal containing information read out therefrom. The optical head 24outputs the RF signal to the amplifier unit 26. The amplifier unit 26enlarges the RF signal from the optical head 24. The amplifier unit 26generates a main reproduced signal from the enlarged RF signal. Inaddition, the amplifier unit 26 generates a servo error signal (trackingand focusing servo error signals) from the output signal of the opticalhead 24. The amplifier unit 26 includes an equalizer for optimizing thefrequency aspect of the main reproduced signal. Also, the amplifier unit26 includes a PLL (phase locked loop) circuit for extracting a bit clocksignal from the equalized main reproduced signal, and for generating aspeed servo signal from the equalized main reproduced signal.Furthermore, the amplifier unit 26 includes a jitter generator forcomparing the time bases of the bit clock signal and the equalized mainreproduced signal, and for detecting jitter components from the resultsof the time-base comparison. A signal of the detected jitter componentsis transmitted from the amplifier unit 26 to the system controller 12.The tracking and focusing servo signals and the speed servo signal aretransmitted from the amplifier unit 26 to the servo processor 16. Theequalized main reproduced signal is transmitted from the amplifier unit26 to the signal processor 14.

[0107] The servo processor 16 receives the speed servo signal and thetracking and focusing servo signals from the amplifier unit 26. Theservo processor 16 receives the rotation servo signals from the spindlemotor 20 via the driver 18. In response to these servo signals, theservo processor 16 implements corresponding servo control processes.

[0108] Specifically, the servo processor 16 generates a rotation controlsignal on the basis of the speed servo signal and the rotation servosignals. The rotation control signal is transmitted from the servoprocessor 16 to the spindle motor 20 via the driver 18. The spindlemotor 20 rotates at a speed depending on the rotation control signal.The rotation control signal is designed to rotate the optical disc 22 ata selected constant linear velocity or a given constant linear velocity.

[0109] In addition, the servo processor 16 generates servo controlsignals on the basis of the focusing and tracking servo signals. Theservo control signals are transmitted from the servo processor 16 to the2-axis actuator in the optical head 22 via the driver 18. The 2-axisactuator controls the laser spot on the optical disc 22 in response tothe servo control signals, and thereby implements focusing and trackingof the laser spot with respect to the optical disc 22.

[0110] During the playback mode of operation of the apparatus, thesignal processor 14 receives the main reproduced signal from theamplifier unit 26. The signal processor 14 is controlled by the systemcontroller 12, thereby converting the main reproduced signal into acorresponding reproduced digital signal. The signal processor 14 detectsa sync signal from the reproduced digital signal. The signal processor14 decodes an 8-16 modulation-resultant signal of the reproduced digitalsignal into NRZ data, that is, non-return-to-zero data. The signalprocessor 14 subjects the NRZ data to an error correction process forevery correction block (every ECC block), thereby generating a sectoraddress signal and first and second information signals. The sectoraddress signal represents the address of a currently-accessed sector onthe optical disc 22. The sync signal and the sector address signal arefed from the signal processor 14 to the system controller 12.

[0111] During the playback mode of operation of the apparatus, thesignal processor 14 temporarily stores the first and second informationsignals in the memory 28. Thus, the signal processor 14 writes the firstand second information signals into the memory 28, and reads the firstand second information signals therefrom. Writing and reading the firstand second information signals into and from the memory 28 arecontrolled to absorb a time-domain change in the transfer rates of thefirst and second information signals. The memory 28 includes, forexample, a D-RAM having a capacity of 64 Mbytes. The signal processor 14outputs the readout signal (the first and second information signalsread out from the memory 28) to the audio-video encoding and decodingunit 30.

[0112] In the case where the first and second information signals fedfrom the memory 28 via the signal processor 14 are compressed data (forexample, MPEG2 data) in which audio data and video data are multiplexed,the audio-video encoding and decoding unit 30 separates the first andsecond information signals into compressed audio data and compressedvideo data. The audio-video encoding and decoding unit 30 expands anddecodes the compressed audio data into non-compressed audio data. Inaddition, the audio-vide encoding and decoding unit 30 expands anddecodes the compressed video data into non-compressed video data. Duringthe expansively decoding process, the audio-video encoding and decodingunit 30 temporarily stores signals and data in the memory 32. The memory32 includes, for example, a D-RAM having a capacity of 64 Mbytes. Theaudio-video encoding and decoding unit 30 converts the non-compressedaudio data into a corresponding analog audio signal throughdigital-to-analog conversion. Also, the audio-video encoding anddecoding unit 30 converts the non-compressed video data into acorresponding analog video signal through digital-to-analog conversion.The audio-video encoding and decoding unit 30 applies the analog audiosignal and the analog video signal to the input/output terminal 34. Theanalog audio signal and the analog video signal are transmitted to anexternal via the input/output terminal 34.

[0113] The data rate of the expansively decoding process by theaudio-video encoding and decoding unit 30, that is, the data transferrate (the data transmission rate) in the expansively decoding process,is equalized to an expansion data rate which is set in accordance withthe type of the related recording mode of operation of the apparatus.Specifically, the audio-video encoding and decoding unit 30 canimplement the expansively decoding process at an expansion data ratewhich can be changed among plural different expansion data rates. Theaudio-video encoding and decoding unit 20 selects one from among theplural different expansion data rates as a desired expansion data ratein accordance with the type of the related recording mode of operationof the apparatus. The audio-video encoding and decoding unit 30 executesthe expansively encoding process at the desired expansion data rate.Information of the type of the recording mode of operation of theapparatus is recorded on the optical disc 22 as control data. During aninitial stage of the playback of the optical disc 22, the control dataare read out therefrom before being transmitted to the system controller12. The system controller 12 sets the expansion data rate in theaudio-video encoding and decoding unit 30 in accordance with the controldata.

[0114] When the apparatus is required to start to operate in therecording mode, the key input unit 10 is actuated to generate therecording start command signal. The recording start command signal istransmitted from the key input unit 10 to the system controller 12. Thesystem controller 12 controls the servo processor 16 and the amplifierunit 26 in response to the recording start command signal, therebystarting the recording mode of operation of the apparatus. The controlof the servo processor 16 includes steps of controlling the driver 18.Firstly, the system controller 12 starts rotation of the optical disc 22and application of a laser spot thereon through the control of thedriver 18. The optical head 24 is controlled by the driver 18, therebyreading out address information from the optical disc 22. The readoutaddress information is transmitted from the optical head 24 to thesystem controller 12 via the amplifier unit 26. The system controller 12finds or decides a target sector (a target track portion), on which asignal is to be recorded, by referring to the address information. Thesystem controller 12 controls the optical head 24 via the servoprocessor 16 and the driver 18, thereby moving the laser spot to thetarget sector on the optical disc 22. During the recording mode ofoperation of the apparatus, the target sector is repetitively changedfrom one to another.

[0115] During the recording mode of operation of the apparatus, an audiosignal and a video signal to be recorded are fed via the input/outputterminal 34 to the audio-video encoding and decoding unit 30. Theaudio-video encoding and decoding unit 30 converts the audio signal intocorresponding audio data through analog-to-digital conversion. Inaddition, the audio-video encoding and decoding unit 30 converts thevideo signal into corresponding video data through analog-to-digitalconversion. The audio-video encoding and decoding unit 30 compressivelyencodes the audio data and the video data into compressed audio data andcompressed video data (for example, MPEG2 audio data and MPEG2 videodata) at a rate depending on the type of the recording mode. Theaudio-video encoding and decoding unit 30 multiplexes the compressedaudio data and the compressed video data to form multiplexed contentsdata. The audio-vide encoding and decoding unit 30 outputs themultiplexed contents data to the signal processor 14. The data rate ofthe compressively encoding process by the audio-video encoding anddecoding unit 30, that is, the data transmission rate in thecompressively encoding process, is equalized to a compression data ratewhich is selected from among plural different rates in accordance withthe type of the recording mode of operation of the apparatus. During thecompressively encoding process, the audio-video encoding and decodingunit 30 temporarily stores data in the memory 32.

[0116] During the recording mode of operation of the apparatus, thesignal processor 14 adds error correction code signals (ECC signals orPI and PO signals) to the multiplexed contents data. The signalprocessor 12 subjects the ECC-added data to NRZ and 8-16 modulationencoding processes. The signal processor 14 adds a sync signal to theencoding-resultant contents data to form sync-added contents data. Thesync signal is fed from the system controller 12. The sync-addedcontents data are temporarily stored in the memory 28. The sync-addedcontents data are read out from the memory 28 at a data ratecorresponding to a data rate of signal recording on the optical disc 22.The signal processor 14 subjects the readout contents data to givenmodulation for record. The signal processor 14 outputs themodulation-resultant signal to the amplifier unit 26. The output signalof the signal processor 14 is an 8-16 modulation-resultant signal. Theamplifier unit 26 corrects the waveform of the output signal of thesignal processor 14. The amplifier unit 26 generates a laser drivesignal in response to the waveform-correction-resultant signal. Theamplifier unit 26 outputs the laser drive signal to the optical head 24.The optical head 24 records the output signal of the amplifier unit 26on the target sector (the target track portion) on the optical disc 22.

[0117] As shown in FIG. 11, the amplifier unit 26 includes a servo errorsignal generation circuit 49, an RF amplifier 50, an equalizer 52, a PLLcircuit 54, a jitter signal generation circuit 56, a laser drive circuit58, a waveform correction circuit 60, a switch 62, a test patterngeneration circuit 64, a temperature detection circuit 66, an asymmetrydetection circuit 70, a PLL circuit 71, a wobble detection circuit 72,an address detection circuit 73, and a timing signal generation circuit74.

[0118] The servo error signal generation circuit 49 is connected to theoptical head 24, the servo processor 16, the wobble detection circuit72, and the address detection circuit 73. The wobble detection circuit72 is connected to the PLL circuit 71. The PLL circuit 71 is connectedto the timing signal generation circuit 74 and the signal processor 14.The address detection circuit 73 is connected to the timing signalgeneration circuit 74, the system controller 12, and the signalprocessor 14. The timing signal generation circuit 74 is connected tothe jitter signal generation circuit 56, the asymmetry detection circuit70, the test pattern generation circuit 64, the system controller 12,and the signal processor 14.

[0119] The RF amplifier 50 is connected to the optical head 24, theequalizer 52, and the asymmetry detection circuit 70. The equalizer 52is connected to the PLL circuit 54. The PLL circuit 54 is connected tothe jitter signal generation circuit 56 and the signal processor 14. Thejitter signal generation circuit 56 is connected to the systemcontroller 12. The asymmetry detection circuit 70 is connected to thesystem controller 12.

[0120] The switch 62 is connected to the waveform correction circuit 60,the test pattern generation circuit 64, the system controller 12, andthe signal processor 14. The test pattern generation circuit 64 isconnected to the system controller 12. The waveform correction circuit60 is connected to the laser drive circuit 58 and the system controller12. The laser drive circuit 58 is connected to the optical head 24 andthe system controller 12. The temperature detection circuit 66 isconnected to the temperature sensor 36 and the system controller 12. Thetemperature detection circuit 66 is an interface between the temperaturesensor 36 and the system controller 12. A signal representative of theambient temperature of the optical disc 22 is transmitted from thetemperature sensor 36 to the system controller 12 via the temperaturedetection circuit 66. The temperature sensor 36 may be replaced by atemperature5 responsive semiconductor such as a temperature-responsivediode provided in the amplifier unit 26. In this case, the temperaturedetection circuit 66 receives a signal generated by thetemperature-responsive semiconductor.

[0121] The amplifier unit 26 operates as follows. The servo error signalgeneration circuit 49 in the amplifier unit 26 produces a servo errorsignal from the output signal of the optical head 24. The servo errorsignal generation circuit 49 outputs the servo error signal to the servoprocessor 16. During the playback mode of operation of the apparatus,the RF amplifier 50 enlarges the output signal of the optical head 24.The RF amplifier 50 outputs the enlarged signal to the equalizer 52 andthe asymmetry detection circuit 70. The equalizer 52 optimizes thefrequency aspect of the enlarged signal. The equalizer 52 outputs theresultant signal to the PLL circuit 54. The PLL circuit 54 subjects theoutput signal of the equalizer 52 to PLL control, thereby generatingreproduced data (read data), a bit clock signal, and a speed servosignal (a signal representing the rotational speed of the optical disc22). The PLL circuit 54 outputs the reproduced data (the read data) tothe jitter signal generation circuit 56 and the signal processor 14. ThePLL circuit 54 outputs the bit clock signal to the jitter signalgeneration circuit 56. The PLL circuit 54 outputs the speed servo signalto the servo processor 16. The jitter signal generation circuit 56compares the time bases of the reproduced data and the bit clock signal,thereby detecting jitter components and generating a signal of thedetected jitter components. The jitter signal generation circuit 56outputs the signal of the jitter components to the system controller 12.The timing of the jitter detection by the jitter signal generationcircuit 56 is controlled by the timing signal generation circuit 74.

[0122] The output signal of the RF amplifier 50 contains a reproduced8-16 modulation-resultant signal during the playback mode of operationof the apparatus. The asymmetry detection circuit 70 decides, from theoutput signal of the RF amplifier 50, the position of the center of ashortest-period signal “3T” relative to the peak and bottom amplitudepositions of a longest-period signal “11T” of the reproduced 8-16modulation-resultant signal. The asymmetry detection circuit 70 informsthe system controller 12 of the decision result as a detected asymmetryvalue. The decision by the asymmetry detection circuit 70 corresponds tothe detection of an asymmetry. The timing of the asymmetry detection bythe asymmetry detection circuit 70 is controlled by the timing signalgeneration circuit 74. The wobble detection circuit 72 generates awobble signal (a frequency signal) from an output signal of the servoerror signal generation circuit 49. The wobble detection circuit 72outputs the wobble signal to the PLL circuit 71. The PLL circuit 71generates a spindle speed signal and a recording clock signal inresponse to the wobble signal. The PLL circuit 71 outputs the spindlespeed signal and the recording clock signal to the timing signalgeneration circuit 74 and the system controller 12. The addressgeneration circuit 73 produces a signal of an address on the opticaldisc 22 and a recording/reproduction timing signal (a land pre-pitsignal or an LPP signal) in response to the output signal of the servoerror signal generation circuit 49. The address generation circuit 73outputs the recording/reproduction timing signal to the timing signalgeneration circuit 74. The address generation circuit 73 outputs theaddress signal and the recording/reproduction timing signal to thesystem controller 12 and the signal processor 14. The timing signalgeneration circuit 74 produces a reproduction timing signal in responseto the output signals from the PLL circuit 71 and the address detectioncircuit 73. The timing signal generation circuit 74 outputs thereproduction timing signal to the jitter signal generation circuit 56and the asymmetry detection circuit 70, thereby controlling the timingof the jitter detection by the jitter signal generation circuit 56 andthe timing of the asymmetry detection by the asymmetry detection circuit70.

[0123] The laser drive circuit 58 in the amplifier unit 26 generates alaser drive signal. The laser drive circuit 58 outputs the laser drivesignal to the semiconductor laser within the optical head 24. Thesemiconductor laser emits the laser beam in response to the laser drivesignal. The optical head 24 includes a photodiode exposed to a portionof the laser beam emitted by the semiconductor laser. The photodiodemonitors the laser beam. The photodiode is also referred to as themonitor diode. The photodiode generates a signal representing theintensity (or the power) of the laser beam. The photodiode feeds thelaser intensity signal back to the laser drive circuit 58 in theamplifier unit 26. The laser drive circuit 58 controls the laser drivesignal in response to the laser intensity signal. The semiconductorlaser, the photodiode, and the laser drive circuit 58 compose an APC(automatic power control) circuit for regulating the power of the laserbeam at a desired level controlled by the system controller 12. The APCcan be selectively enabled and disabled by the system controller 12. Forexample, the APC is enabled during the playback mode of operation of theapparatus, and is disabled during the recording mode of operation of theapparatus. The laser drive circuit 58 transmits the laser intensitysignal to an A/D converter within the system controller 12. Thus, theintensity of the laser beam can be monitored by the system controller12.

[0124] During the recording mode of operation of the apparatus, thetiming signal generation circuit 74 produces a timing signal. The timingsignal generation circuit 74 outputs the timing signal to the testpattern generation circuit 64, the system controller 12, and the signalprocessor 14. The test pattern generation circuit 64 produces a signalof a test pattern in response to the output signal from the timingsignal generation circuit 74 while being controlled by the systemcontroller 12. The test pattern generation circuit 64 outputs the testpattern signal to the switch 62. The switch 62 receives the 8-16modulation-resultant signal (the write data or the contents data to berecorded) from the signal processor 14. The switch 62 is controlled bythe system controller 12, selecting one of the test pattern signal andthe 8-16 modulation-resultant signal and outputting the selected signalto the waveform correction circuit 60. The waveform correction circuit60 converts the waveform of the output signal of the switch 62 into oneof waveforms basically similar to the recording waveform WA and awaveform equivalent to the recording waveform WB. The waveformcorrection circuit 60 uses waveform correction parameters whichdetermine the recording power level Pp, the erasing power level Pb, andthe time intervals Ta, Th, Tc, and Td in the recording waveform WA. Atleast one of the waveform correction parameters used by the waveformcorrection circuit 60 can be changed so that the waveform of the signalgenerated thereby can be changed among those basically similar to therecording waveform WA. The waveform correction parameters used by thewaveform correction circuit 60 can be changed by the system controller12. The waveforms basically similar to the recording waveform WA aredifferent from each other. Accordingly, these waveforms providedifferent statuses of the power conditions (the intensity conditions) ofthe laser beam respectively. One of the different statuses of the powerconditions of the laser beam is selected through the control of thewaveform correction circuit 60 by the system controller 12.

[0125]FIG. 29 shows an example of the waveform correction circuit 60.The waveform correction circuit 60 in FIG. 29 includes waveformconverters 60A1, 60A2, 60A3, 60A4, 60A5, 60A6, 60A7, 60A8, and 60B, anda switch 60C. The input terminals of the waveform converters 60A1-60A8,and 60B are connected to the switch 62 (see FIG. 11). The outputterminals of the waveform converters 60A1-60A8, and 60B are connected tothe switch 60C. The switch 60C is connected to the laser drive circuit58 (see FIG. 11). The switch 60C has a control terminal connected to thesystem controller 12 (see FIG. 9).

[0126] The waveform converters 60A1-60A8 in the waveform correctioncircuit 60 change the output signal of the switch 62 into pulse trainsignals having waveforms basically similar to the recording waveform WA(see FIG. 3). The waveform converters 60A1-60A8 output the pulse trainsignals to the switch 60C. The pulse train signals generated by thewaveform converters 60A1-60A8 are different from each other in at leastone of waveform correction parameters. The waveform correctionparameters include a parameter determining the recording power level Ppof the laser beam, a parameter determining the erasing power level Pb ofthe laser beam, a parameter determining the time interval Ta, aparameter determining the time interval Th, a parameter determining thetime interval Tc, and a parameter determining the time interval Td (seeFIG. 3). The recording power level Pp, the erasing power level Pb, andthe time intervals Ta, Th, Tc, and Td vary as the values of the waveformcorrection parameters change.

[0127] The power conditions (the intensity conditions) of the laser beamdepend on the recording power level Pp, the erasing power level Pb, andthe time intervals Ta, Tb, Tc, and Td. Accordingly, the waveformconverters 60A1, 60A2, 60A3, 60A4, 60A5, 60A6, 60A7, and 60A8 correspondto eight different statuses P1, P2, P3, P4, P5, P6, P7, and P8 of thepower conditions of the laser beam, respectively. As understood from theprevious description, the waveform converters 60A1-60A8 have respectiveeight different sets of the waveform correction parameters. Each of thewaveform converters 60A1-60A8 may use a known circuit.

[0128] The waveform converter 60B in the waveform correction circuit 60changes the output signal of the switch 62 into a pulse signal having awaveform equivalent to the recording waveform WB (see FIG. 3). Thewaveform converter 60B includes a pulse-width shortening circuit.Specifically, the waveform converter 60B includes a delay element and anAND circuit. The delay element defers the output signal of the switch62. The AND circuit executes AND operation between the output signal ofthe delay element and the output signal of the switch 62, therebygenerating the pulse signal. The waveform converter 60B outputs thepulse signal to the switch 60C.

[0129] The switch 60C in the waveform correction circuit 60 selects onefrom among the output signals of the waveform converters 60A1-60A8, and60B in response to a control signal fed from the system controller 12.The switch 60C transmits the selected signal to the laser drive circuit58. The laser drive circuit 58 converts the selected signal into acorresponding laser drive signal. When the switch 60C selects one of theoutput signals of the waveform converters 60A1-60A8, the laser beamemitted by the semiconductor laser has a waveform basically similar tothe recording waveform WA (see FIG. 3). At this time, the powerconditions (the intensity conditions) of the laser beam agree with oneof the eight different statuses P1-P8 which corresponds to thewaveform-converter output signal selected by the switch 60C. Thus, thepower conditions of the laser beam can be changed among the eightdifferent statuses P1-P8 as the switch 60C is controlled by the systemcontroller 12 to sequentially select one of the output signals of thewaveform converters 60A1-60A8. When the switch 60C selects the outputsignal of the waveform converter 60B, the laser beam emitted by thesemiconductor laser has the recording waveform WB (see FIG. 3).

[0130] As will be made clear later, during the recording mode ofoperation of the apparatus except a short term of the execution of awaveform correction optimizing process, the switch 60C selects one fromamong the output signals of the waveform converters 60A1-60A8, and 60Bwhich is designated by the system controller 12.

[0131] The selection-object designated signal can be changed by thesystem controller 12 in response to the results of the waveformcorrection optimizing process. The new designated one of the outputsignals of the waveform converters 60A1-60A8, and 60B is selected by theswitch 60C, and is used during the recording mode of operation of theapparatus which follows the term of the execution of the waveformcorrection optimizing process.

[0132] With reference back to FIG. 11, the switch 62 is controlled bythe system controller 12 to provide a time base change in a great unit.The waveform correction circuit 60 responds to the time base change. Aswill be made clear later, the waveform correction parameters whichdetermine the laser power levels Pp and Pb, and the time intervals Ta,Th, Tc, and Td (see FIG. 3) and which are used by the waveformcorrection circuit 60 are set so as to optimize the asymmetry value (orthe asymmetry value and the jitter value).

[0133] The test pattern signal generated by the test pattern generationcircuit 64 has the alternation of the lowest-frequency signal (thelongest-period signal) “11T” and the highest-frequency signal (theshortest-period signal) “3T” of the 8-16 modulation-resultant signal.With reference to FIG. 12, the test pattern signal is selected by theswitch 62 for a time interval corresponding to one ECC block. Test dataoriginating from the test pattern signal are recorded on an ECC blockhaving an address A2. The ECC block is composed of 16 successivesectors. The ECC block loaded with the test data is also referred to asthe test ECC block. The lowestfrequency signal “11T” is recorded on thefirst sector, that is, the B0 sector in the test ECC block. Thehighest-frequency signal “3T” is recorded on the second sector, that is,the B1 sector in the test ECC block. The lowest-frequency signal “11T”is recorded on the third sector, that is, the B2 sector in the test ECCblock. The highest-frequency signal “3T” is recorded on the fourthsector, that is, the B3 sector in the test ECC block. Similarly, thelowestfrequency signal “11T” and the highest-frequency signal “3T” arealternately recorded on the fifth and later sectors in the test ECCblock. Thus, eight sets of the lowest-frequency signal “11T” and thehighest-frequency signal “3T” are assigned to eight pairs of twosuccessive sectors, respectively. During the recording of the test data,the system controller 12 changes the switch 60C within the waveformcorrection circuit 60 so that the power conditions (the intensityconditions) of the laser beam are changed among the eight differentstatuses P1, P2, . . . , and P8. The eight power statuses P1, P2, . . ., and P8 are used for the eight sets of the lowest-frequency signal“11T” and the highest-frequency signal “3T”, respectively.

[0134] During the playback mode of operation of the apparatus, thesystem controller 12 detects an access to the test ECC block. The timingsignal generation circuit 74 produces timing pulses T0, T1, T2, T3, . .. corresponding to the front ends of the sectors in the test ECC blockrespectively (see FIG. 12). The asymmetry detection circuit 70 samplesand holds the output signal of the RF amplifier 50 in response to thetiming pulses T0, T1, T2, T3, . . . fed from the timing signalgeneration circuit 74. Specifically, the asymmetry detection circuit 70samples and holds a peak PDP1 and a bottom PDB1 of the lowest-frequencysignal “11T” reproduced from the B0 sector in the test ECC block. Theasymmetry detection circuit 70 samples and holds a center level PDC1 ofthe highest-frequency signal “3T” reproduced from the B1 sector in thetest ECC block. Similarly, the asymmetry detection circuit 70 samplesand holds peaks and bottoms of the lowest-frequency signals “11T” andcenter levels of the highest-frequency signals “3T” reproduced from thelater sectors in the test ECC block. Thus, a peak and a bottom PDB1 ofthe lowest-frequency signal “11T”, and a center level of thehighest-frequency signal “3T” are detected for each of the eightdifferent-power sets of the lowest-frequency signal “11T” and thehighest-frequency signal “3T”. The asymmetry detection circuit 70converts the sample-and-hold results into digital data representing thedetected asymmetries for the respective eight different-power-statussets of the lowest-frequency signal “11T” and the highest-frequencysignal “3T”. The asymmetry detection circuit 70 outputs the asymmetrydata to the system controller 12.

[0135] During the recording of contents information on the optical disc22, the system controller 12 sets the disc-scanning linear velocity toone from among different values through the speed control of the spindlemotor 20. The different velocity values include 6 m/s corresponding to arecording time of about 2 hours and a high picture quality, 3 m/scorresponding to a recording time of about 4 hours and a normal picturequality, and 1.5 m/s corresponding to a recording time of about 8 hoursand a low picture quality.

[0136] According to a first example, one of the waveform converters60A1-60A8 in the waveform correction circuit 60 which provide recordingwaveforms basically similar to the recording waveform WA (see FIG. 3) isselected as an active waveform converter for disc-scanning linearvelocities of 1.5 m/s and 3 m/s. On the other hand, the waveformconverter 60B in the waveform correction circuit 60 which provides therecording waveform WB (see FIG. 3) is selected as an active waveformconverter for a disc-scanning linear velocity of 6 m/s.

[0137] According to a second example, one of the waveform converters60A1-60A8 in the waveform correction circuit 60 which provide recordingwaveforms basically similar to the recording waveform WA (see FIG. 3) isselected as an active waveform converter for disc-scanning linearvelocities of 1.5 m/s, 3 m/s, and 6 m/s.

[0138] The contents-information recording time can be varied by changingnot only the disc-scanning linear velocity but also the compression datarate used by the audio-video encoding and decoding unit 30. The transferrate of the signal recorded on the optical disc 22 is set higher thanthe transfer rate of the compression-resultant data which corresponds tothe highest compression data rate. The difference between the transferrates is absorbed by the memory 28.

[0139] The CLV control of the optical disc 22 may be replaced by CAVcontrol or zone CAV control. In this case, even when aninner-circumference linear velocity and an outer-circumference linearvelocity are changed for about 30 zones, the system controller 12manages address positions on a recording track and sets an actual linearvelocity for each of the address positions. In addition, the period T ofthe bit clock signal is set on the basis of the set linear velocity.

[0140] With reference to FIG. 13, time intervals “a” alternate with timeintervals “b”. During the time intervals “a”, a signal is written intothe memory 28 at a first transfer rate. During the time intervals “b”,the signal is read out from the memory 28 at a second transfer ratehigher than the first transfer rate before being recorded on the opticaldisc 22. The upper side of the occupancy of the memory 28 is limited toa full level. The full level is set in response to the compression datarate or an externally applied signal. After an initial stage, the lowerside of the occupancy of the memory 28 is limited to an empty level.

[0141] The system controller 12 operates in accordance with a programstored in its internal ROM. According to the program, the systemcontroller 12 decides which of a recording mode, a playback mode, and awaiting mode the required mode of operation of the apparatus is equalto. When the required mode is equal to the recording mode, the programadvances to a segment corresponding to the recording mode. When therequired mode is equal to the playback mode, the program advances to asegment corresponding to the playback mode. When the required mode isequal to the waiting mode, the program advances to a segmentcorresponding to the waiting mode.

[0142]FIG. 14 is a flowchart of the program segment corresponding to therecording mode. With reference to FIG. 14, a first step SB of theprogram segment activates the audio-video encoding and decoding unit 30and the signal processor 14 to generate processing-resultant contentsdata (processing-resultant audio and video data to be recorded). Thefirst step SB controls the signal processor 14 to write theprocessing-resultant contents data into the memory 28. After the stepSB, the program advances to a step SC.

[0143] The step SC decides whether or not the degree of the occupancy ofthe memory 28 has reached the full level. When the degree of theoccupancy of the memory 28 has reached the full level, the programadvances from the step SC to a step SD. Otherwise, the program returnsfrom the step SC to the step SB.

[0144] The step SD controls the signal processor 14 to read out thecontents data from the memory 28. The step SD controls the amplifierunit 26 to transmit the readout contents data from the memory 28 to theoptical head 24. The contents data are recorded on the optical disc 22by the optical head 24.

[0145] A step SE following the step SD decides whether or not the degreeof the occupancy of the memory 28 has reached the empty level. When thedegree of the occupancy of the memory 28 has reached the empty level,the program advances from the step SE to a step SF. Otherwise, theprogram returns from the step SE to the step SD.

[0146] The step SF controls the signal processor 14 to suspend readingout the contents data from the memory 28. After the step SF, the programadvances to a step SG.

[0147] The step SG decides whether or not a waveform correctionoptimizing process should be executed. In the case where the waveformcorrection optimizing process has not been executed yet after theplacement of the present optical disc 22 in position within theapparatus, the step SG decides that the waveform correction optimizingprocess should be executed. On the other hand, in the case where thewaveform correction optimizing process has been executed, the step SGdecides that the waveform correction optimizing process should not beexecuted. When it is decided that the waveform correction optimizingprocess should be executed, the program advances from the step SG to astep SH. When it is decided that the waveform correction optimizingprocess should not be executed, the program returns from the step SG tothe step SC.

[0148] The step SH memorizes or stores the address of a position (an ECCblock) on the optical disc 22 which should be accessed next for therecording of the contents data.

[0149] A block SI following the step SH changes the operation of theapparatus to a test mode to execute the waveform correction optimizingprocess.

[0150] A step SJ subsequent to the block SI returns the operation of theapparatus to the recording mode. The step SJ controls the servoprocessor 16 in response to the address stored by the step SH so thatthe optical head 24 will kick back to the position on the optical disc22 which should be accessed next for the recording of the contents data.After the step SJ, the program returns to the step SC.

[0151] It should be noted that the step SG may be omitted from theprogram segment in FIG. 14. In this case, the step SF is immediatelyfollowed by the step SH.

[0152] As shown in FIG. 15, a first step SIa in the block SI detects theaddress of a position (an ECC block) on the optical disc 22 whichimmediately follows the address of the last accessed position loadedwith the contents data. The ECC block address A2 in FIG. 12 correspondsto the address detected by the step SIa while the ECC block address A1in FIG. 12 corresponds to the address of the last accessed positionloaded with the contents data. A step SIb subsequent to the step SIacontrols the amplifier unit 26 to record the test pattern signal on thedisc position (the ECC block) whose address is detected by the step SIa.The ECC block loaded with the test pattern signal is also referred to asthe test ECC block. Specifically, the step SIb controls the switch 62within the amplifier unit 26 to select the test pattern signal fed fromthe test pattern generation circuit 64.

[0153] As previously mentioned, the test pattern signal has thealternation of the lowest-frequency signal (the longest-period signal)“11T” and the highest-frequency signal (the shortest-period signal) “3T”of the 8-16 modulation-resultant signal. As shown in FIG. 12, thelowest-frequency signal “11T” is recorded on the first sector, that is,the B0 sector in the test ECC block. The highest-frequency signal “3T”is recorded on the second sector, that is, the B1 sector in the test ECCblock. The lowest-frequency signal “11T” is recorded on the thirdsector, that is, the B2 sector in the test ECC block. Thehighest-frequency signal “3T” is recorded on the fourth sector, that is,the B3 sector in the test ECC block. Similarly, the lowest-frequencysignal “11T” and the highest-frequency signal “3T” are alternatelyrecorded on the fifth and later sectors in the test ECC block. Thus,eight sets of the lowest-frequency signal “11T” and thehighest-frequency signal “3T” are assigned to eight pairs of twosuccessive sectors, respectively.

[0154] The step SIb controls the waveform correction circuit 60 tochange the power conditions (the intensity conditions) of the laser beamamong the eight different statuses P1, P2, . . . , and P8. Specifically,the step SIb changes at least one of the waveform correction parametersin the waveform correction circuit 60 among eight different values. Asshown in FIG. 12, the eight power statuses P1, P2, , and P8 are used forthe eight sets of the lowest-frequency signal “11T” and thehighest-frequency signal “3T”, respectively. The laser-beam powercondition change is accorded with one of a monotonically increasingpattern, a monotonically decreasing pattern, a pattern in which thepower level is alternately changed between a positive side and anegative side of a predetermined value, a pattern in which the powerlevel is changed in correspondence with the detected temperature, apattern in which the power level is changed with the record position,predetermined different patterns corresponding to the lapse of time fromthe previous recording, and different patterns depending on theconditions of the apparatus.

[0155] A step SIc following the step SIb controls the servo processor 16so that the optical head 24 will kick back to the front end of the testECC block on the optical disc 22. After the step SIc, the programadvances to a step SId.

[0156] A step SId changes the operation of the apparatus to the playbackmode. The step SId controls the optical head 24 via the amplifier unit26 to reproduce the test pattern signal from the test ECC block. Thestep SId receives the data from the amplifier unit 26 which representthe detected asymmetries for the respective eightdifferent-power-condition sets of the lowest-frequency signal “11T” andthe highest-frequency signal “3T”. The received asymmetry data containinformation of the detected peak and the detected bottom of thelowest-frequency signal “11T”, and the center level of thehighest-frequency signal “3T” for each of the eightdifferent-power-status sets of the lowest-frequency signal “11T” and thehighest-frequency signal “3T”.

[0157] A step SIe calculates the error (the deviation or difference) ofthe center level of the highest-frequency signal “3T” from the centerbetween the detected peak and the detected bottom of thelowest-frequency signal “11T” for each of the eightdifferent-power-status sets of the lowest-frequency signal “11T” and thehighest-frequency signal “3T”. The step SIe compares the calculatederrors, and thereby detects the smallest of the calculated errors. Thestep SIe selects one from among the eight different-power-status sets ofthe lowest-frequency signal “11T” and the highest-frequency signal “3T”which corresponds to the smallest error. In other words, the step SIeselects one from among the eight different recording power statuseswhich corresponds to the smallest error. The step SIe identifies thevalue of the waveform correction parameter (or the values of thewaveform correction parameters) in the waveform correction circuit 60which corresponds to the selected one of the eight different recordingpower statuses. Specifically, the step SIe identifies one of thewaveform converters 60A1-60A8 in the waveform correction circuit 60which corresponds to the selected one of the eight different recordingpower statuses.

[0158] A step SIf subsequent to the step SIe decides whether or not theidentified value of the waveform correction parameter (or the identifiedvalues of the waveform correction parameters) is equal to the parametervalue which is currently set in the waveform correction circuit 60 forthe recording of the contents data. When the identified value is notequal to the currently-set parameter value, the program advances fromthe step SIf to a step SIg. When the identified value is equal to thecurrently-set parameter value, the program jumps from the step SIf tothe step SJ in FIG. 14. Specifically, the step SIf decides whether ornot the identified waveform converter is the same as that currently setactive for the recording of the contents data (the currently designatedwaveform converter). When the identified waveform converter is the sameas that currently set active, the program jumps from the step SIf to thestep SJ in FIG. 14. Otherwise, the program advances from the step SIf tothe step SIg.

[0159] The step SIg updates or changes the waveform correction parameteror parameters in the waveform correction circuit 60 to the identifiedvalue or values. Specifically, the step SIg controls the switch 60C inthe waveform correction circuit 60 to select the output signal of one ofthe waveform converters 60A1-60A8 which is the same as the identifiedwaveform converter. The selected waveform-converter output signal isused for later recording of the contents data. After the step SIg, theprogram advances to the step SJ in FIG. 14.

[0160] As shown in FIG. 12, the contents data are recorded on the ECCblock at the address A1 by the step SD (see FIG. 14). The test patternsignal is recorded on the ECC block at the address A2 by the step SIb(see FIG. 15). The address A2 immediately follows the address A1. Therecording of the contents data on the ECC block at the address A1 iscontinuously followed by the recording of the test pattern signal on thenext ECC block at the address A2. Thus, a waiting time is prevented fromoccurring between the recording of the contents data and the subsequentrecording of the test pattern signal. As previously mentioned, the testpattern signal is reproduced from the ECC block at the address A2 toimplement the waveform correction optimizing process. Then, the opticalhead 24 is moved back to the front end of the ECC block at the addressA2. Subsequently, the contents data are recorded on the ECC block at theaddress A2 by the step SD (see FIG. 14). In this case, the contents dataare written over the test pattern signal.

[0161] A 0-kilobyte linking method is applied to the connection betweenthe contents data on the neighboring ECC blocks at the addresses A1 andA2. The 0-kilobyte linking method may use that shown in, for example,Japanese published unexamined patent application 2000-137952 or Japanesepublished unexamined patent application 2000-137948, the disclosure ofwhich is hereby incorporated by reference. According to the 0-kilobytelinking method, the previous contents data and the new contents data arecontinuously recorded in a manner such that the connection between theprevious contents data and the new contents data is located at theboundary between two neighboring ECC blocks. The previous contents dataand the new contents data can be continuously reproduced. As previouslymentioned, the new contents data are written over the test patternsignal. Since the test pattern signal and the new contents data arerecorded in the same recording method, the test pattern signal is fullyerased by the overwriting process.

[0162] With reference back to FIG. 11, the PLL circuit 71 receives thewobble signal from the wobble detection circuit 72. The wobble signalhas a frequency of, for example, 140 kHz. The wobble signal has awaveform shown in FIG. 28. The PLL circuit 71 multiplies the frequencyof the wobble signal, thereby generating the recording clock signalhaving a frequency equal to an integer multiple of the wobble signalfrequency (see FIG. 28). The frequency of the recording clock signal isequal to, for example, 27 MHz. The timing signal generation circuit 74receives the recording clock signal from the PLL circuit 71. Also, thetiming signal generation circuit 74 receives the recording/reproductiontiming signal (the LPP signal) from the address detection circuit 73.The LPP signal has a waveform shown in FIG. 28. A 1-sync-framecorresponding signal is recorded on the optical disc 22 in synchronismwith the LPP signal.

[0163] The timing signal generation circuit 74 counts pulses in therecording clock signal while using a timing given by the LPP signal as areference. Thereby, the timing signal generation circuit 74 producestiming pulses T0, T1, T2, T3, . . . corresponding to the front ends ofthe sectors in the test ECC block respectively (see FIG. 12). The timingsignal generation circuit 74 outputs the timing pulses T0, T1, T2, T3, .. . to the asymmetry detection circuit 70 as a reproduction timingsignal. The timing signal outputted from the timing signal generationcircuit 74 has a waveform shown in FIG. 28.

[0164] As shown in FIG. 16, the asymmetry detection circuit 70 includesa peak hold circuit 601, a bottom hold circuit 602, a low pass filter(an LPF) 603, an A/D converter 604, and a switch 605.

[0165] The peak hold circuit 601, the bottom hold circuit 602, and theLPF 603 receive the output signal of the RF amplifier 50. The peak holdcircuit 601, the bottom hold circuit 602, the LPF 603, and the switch605 receive the reproduction timing signal (the timing pulses) from thetiming signal generation circuit 74.

[0166] The peak hold circuit 601 and the bottom hold circuit 602 arereset at the moment given by the timing pulse TO (see FIG. 12).

[0167] The peak hold circuit 601 holds the peak level of thelowest-frequency signal “11T” which is reproduced from the first sector,that is, the B0 sector in the test ECC block during the time intervalbetween the moments given the timing pulses TO and Ti (see FIG. 12). Thepeak hold circuit 601 outputs a signal representative of the held peaklevel to the switch 605. The bottom hold circuit 602 holds the bottomlevel of the lowest-frequency signal “11T” which is reproduced from thefirst sector in the test ECC block. The bottom hold circuit 602 outputsa signal representative of the held bottom level to the switch 605. TheLPF 603 smooths or averages the highest-frequency signal “3T” which isreproduced from the second sector, that is, the B1 sector in the testECC block during the time interval between the moments given by thetiming pulses T1 and T2 (see FIG. 12). Thus, the LPF 603 generates asignal representing the center level of the highest-frequency signal“3T” reproduced from the second sector in the test ECC block. The LPF603 outputs the center level signal to the switch 605. During a shorttime interval at and around the moment given by the timing pulse T2, theswitch 605 sequentially selects and transmits the peak level signal, thebottom level signal, and the center level signal to the A/D converter604. The A/D converter 604 changes the peak level signal, the bottomlevel signal, and the center level signal into corresponding digitaldata. The A/D converter 604 outputs the digital data to the systemcontroller 12. In this way, the peak level, the bottom level, and thecenter level are detected and are notified to the system controller 12for first one of the eight different-power-status sets of thelowest-frequency signal “11T” and the highest-frequency signal “3T”.Similarly, the peak level, the bottom level, and the center level aredetected and are notified to the system controller 12 for second andlater ones of the eight different-power-status sets of thelowest-frequency signal “11T” and the highest-frequency signal “3T”.

[0168] According to the first embodiment of this invention, during afree time of the optical head 24 in the term of writing contents datainto the memory 28, the test pattern signal is recorded on andreproduced from a disc position to be accessed next for the recording ofthe contents data. The asymmetry of the reproduced test pattern signalis measured. The waveform correction parameters which determine theintensity (the power) of the laser beam are set and adjusted so as tooptimize the measured asymmetry. Thus, the optimal conditions of thesignal recording on the disc position to be accessed next are detectedon a measurement basis. In some cases, the recording sensitivity of theoptical disc 22 varies from disc position to disc position. Therefore,in these cases, the optical recording conditions vary from disc positionto disc position. In the first embodiment of this invention, it ispossible to detect the optimal recording conditions at each of varyingdisc positions. As previously mentioned, the test patten signal iserased since the new contents data are written thereover. Therefore, itis unnecessary to provide an exclusive disc area for storing the testpattern signal. Furthermore, it is unnecessary for the optical head 24to implement seek to the exclusive disc area for storing the testpattern signal. In addition, it is unnecessary to provide a special timeof setting and adjusting the waveform correction parameters.

Second Embodiment

[0169] A second embodiment of this invention is a modification of thefirst embodiment thereof. The second embodiment of this invention uses ablock SGA instead of the step SG in FIG. 14.

[0170] As shown in FIG. 17, the block SGA has a first step 101 followingthe step SF (see FIG. 14). The step 101 decides whether or not a timervalue is smaller than a predetermined value “k”. When the timer value isnot smaller than the predetermined value “k”, that is, when the timervalue is equal to or greater than the predetermined value “k”, theprogram advances from the step 101 to a step 102. When the timer valueis smaller than the predetermined value “k”, the program advances fromthe step 101 to a step 103.

[0171] The step 102 resets the timer value. After the step 102, theprogram advances to the step SH (see FIG. 14).

[0172] The step 103 counts up or increments the timer value by “1”.After the step 103, the program returns to the step SC (see FIG. 14).

Third Embodiment

[0173] A third embodiment of this invention is a modification of thefirst embodiment thereof. The third embodiment of this invention uses ablock SGB instead of the step SG in FIG. 14.

[0174] As shown in FIG. 18, the block SGB has a first step 201 followingthe step SF (see FIG. 14). The step 201 decides whether or not theaddress of a new ECC block for data recording is separate from theaddress of a last test ECC block by at least a predetermined distance (apredetermined address value). When the address of the new ECC block isseparate from the address of the last test ECC block by at least thepredetermined distance, the program advances from the step 201 to a step202. Otherwise, the program returns from the step 201 to the step SC(see FIG. 14).

[0175] The step 202 stores the address of the new ECC block as theaddress of a newest ECC block. After the step 202, the program advancesto the step SH (see FIG. 14).

Fourth Embodiment

[0176] A fourth embodiment of this invention is a modification of thefirst embodiment thereof. The fourth embodiment of this invention uses ablock SGC instead of the step SG in FIG. 14.

[0177] As shown in FIG. 19, the block SGC has a first step 301 followingthe step SF (see FIG. 14). The step 301 decides whether or not thepresent temperature is separate from the temperature, which occurs atthe last execution of the waveform correction optimizing process, by atleast a predetermined value. When the present temperature is separatefrom the temperature, which occurs at the last execution of the waveformcorrection optimizing process, by at least the predetermined value, theprogram advances from the step 301 to a step 302. Otherwise, the programreturns from the step 301 to the step SC (see FIG. 14).

[0178] The step 302 stores information of the present temperature as thetemperature which occurs at the new execution of the waveform correctionoptimizing process. After the step 302, the program advances to the stepSH (see FIG. 14).

Fifth Embodiment

[0179] A fifth embodiment of this invention is a modification of thefirst embodiment thereof. The fifth embodiment of this invention uses ablock SGD instead of the step SG in FIG. 14.

[0180] As shown in FIG. 20, the block SGD has a first step 401 followingthe step SF (see FIG. 14). The step 401 kicks the optical head 24 backto the front end of the last accessed ECC block.

[0181] A step 402 following the step 401 reproduces a signal from theECC block. The step 402 detects jitter of the reproduced signal.

[0182] A step 403 subsequent to the step 402 decides whether or not thedetected jitter exceeds a predetermined value. When the detected jitterexceeds the predetermined value, the program advances from the step 403to the step SH (see FIG. 14). Otherwise, the program returns from thestep 403 to the step SC (see FIG. 14).

Sixth Embodiment

[0183] A sixth embodiment of this invention is a modification of thefirst embodiment thereof. The sixth embodiment of this invention uses ablock SGE instead of the step SG in FIG. 14.

[0184] As shown in FIG. 21, the block SGE has a first step 401Afollowing the step SF (see FIG. 14). The step 401A kicks the opticalhead 24 back to the front end of the last accessed ECC block.

[0185] A step 402A following the step 401A reproduces data from the ECCblock. The step 402A detects the error rate of the reproduced data.

[0186] A step 403A subsequent to the step 402A decides whether or notthe detected error rate exceeds a predetermined value. When the detectederror rate exceeds the predetermined value, the program advances fromthe step 403A to the step SH (see FIG. 14). Otherwise, the programreturns from the step 403A to the step SC (see FIG. 14).

Seventh Embodiment

[0187] A seventh embodiment of this invention is a modification of thefirst embodiment thereof. The seventh embodiment of this invention usesa block SGF instead of the step SG in FIG. 14.

[0188] As shown in FIG. 22, the block SGF has a first step 501 followingthe step SF (see FIG. 14). The step 501 decides whether or not thepresent voltage of the feedback signal from the monitor diode isdifferent from the feedback signal voltage, which occurs at the lastexecution of the waveform correction optimizing process, by at least apredetermined value. When the present voltage of the feedback signal isdifferent from the feedback signal voltage, which occurs at the lastexecution of the waveform correction optimizing process, by at least thepredetermined value, the program advances from the step 501 to a step502. Otherwise, the program returns from the step 501 to the step SC(see FIG. 14).

[0189] The step 502 stores information of the present voltage of thefeedback signal as the feedback signal voltage which occurs at the newexecution of the waveform correction optimizing process. After the step502, the program advances to the step SH (see FIG. 14).

Eighth Embodiment

[0190] An eighth embodiment of this invention is a combination of thesecond and third embodiments thereof. In the eighth embodiment of thisinvention, the waveform correction optimizing process is executed whenthe step 101 decides that the timer value is equal to or greater thanthe predetermined value “k” or when the step 201 decides that theaddress of the new ECC block is separate from the address of the lasttest ECC block by at least the predetermined distance.

Ninth Embodiment

[0191] A ninth embodiment of this invention is a combination of thesecond, third, fourth, fifth, sixth, and seventh embodiments thereof. Inthe ninth embodiment of this invention, the waveform correctionoptimizing process is executed only when at least one of the followingconditions 1), 2), 3), 4), 5), and 6) is satisfied.

[0192] 1) The step 101 decides that the timer value is equal to orgreater than the predetermined value “k”.

[0193] 2) The step 201 decides that the address of the new ECC block isseparate from the address of the last test ECC block by at least thepredetermined distance.

[0194] 3) The step 301 decides that the present temperature is separatefrom the temperature, which occurs at the last execution of the waveformcorrection optimizing process, by at least the predetermined value.

[0195] 4) The step 403 decides that the detected jitter exceeds thepredetermined value.

[0196] 5) The step 403A decides that the detected error rate exceeds thepredetermined value.

[0197] 6) The step 501 decides that the present voltage of the feedbacksignal is different from the feedback signal voltage, which occurs atthe last execution of the waveform correction optimizing process, by atleast the predetermined value.

Tenth Embodiment

[0198] A tenth embodiment of this invention is a combination of thesecond and third embodiments thereof. In the tenth embodiment of thisinvention, the waveform correction optimizing process is executed onlywhen both the following conditions 1) and 2) are satisfied.

[0199] 1) The step 101 decides that the timer value is equal to orgreater than the predetermined value “k”.

[0200] 2) The step 201 decides that the address of the new ECC block isseparate from the address of the last test ECC block by at least thepredetermined distance.

Eleventh Embodiment

[0201] An eleventh embodiment of this invention is a combination of thesecond, third, and fourth embodiments thereof. In the eleventhembodiment of this invention, the waveform correction optimizing processis executed only when at least one of the following conditions 1) and 2)are satisfied.

[0202] 1) The step 101 decides that the timer value is equal to orgreater than the predetermined value “k”. The step 201 decides that theaddress of the new ECC block is separate from the address of the lasttest ECC block by at least the predetermined distance.

[0203] 2) The step 101 decides that the timer value is equal to orgreater than the predetermined value “k”. The step 301 decides that thepresent temperature is separate from the temperature, which occurs atthe last execution of the waveform correction optimizing process, by atleast the predetermined value.

Twelfth Embodiment

[0204] A twelfth embodiment of this invention is a combination of atleast two of the second, third, fourth, fifth, sixth, and seventhembodiments thereof.

Thirteenth Embodiment

[0205] A thirteenth embodiment of this invention is a modification ofone of the first to twelfth embodiments thereof. In the thirteenthembodiment of this invention, the peak level of the lowest-frequencysignal “11T” reproduced from one sector in the test ECC block is sampledand held at each of different time points. The sampled and held peaklevels are averaged into a mean peak level.

[0206] The mean peak level is notified to the system controller.Similarly, the bottom level of the lowest-frequency signal “11T”reproduced from one sector in the test ECC block is sampled and held ateach of different time points. The sampled and held bottom levels areaveraged into a mean bottom level. The mean bottom level is notified tothe system controller.

[0207] The thirteenth embodiment of this invention compensates for avariation in the conditions of the 1-sector-corresponding reproducedsignal which might be caused by noise in the apparatus, unevenness inthe sensitivity of the optical disc 22, and a change in the trackingservo conditions. Therefore, the thirteenth embodiment of this inventionaccurately measures or detects the asymmetry.

Fourteenth Embodiment

[0208] A fourteenth embodiment of this invention is a modification ofone of the first to thirteenth embodiments thereof. The fourteenthembodiment of this invention measures the jitter instead of theasymmetry. The test pattern signal may be a random signal or a portionof the contents data.

[0209] In the fourteenth embodiment of this invention, the test patternsignal is recorded on a test ECC block while the power conditions or theintensity conditions of the laser beam (at least one of the waveformcorrection parameters in the waveform correction circuit 60) are changed2-sector by 2-sector. The test pattern signal is reproduced from thetest ECC block. The jitter of the reproduced signal is measured at atiming similar to the previously-indicated timing for each of the sectorpairs. The smallest of the measured jitters is selected. From among theeight different power conditions (statuses), one is selected whichcorresponds to the smallest jitter. The selected one of the eightdifferent power statuses is used as an optimal power status. Thewaveform correction parameter or parameters in the waveform correctioncircuit 60 are changed in accordance with the optimal power status. Thechange of the waveform correction parameter or parameters may beimplemented by using a predetermined correction coefficient orcoefficients in a table corresponding to the characteristics of theoptical disc 22.

Fifteenth Embodiment

[0210] A fifteenth embodiment of this invention is a modification of oneof the first to fourteenth embodiments thereof. In the fifteenthembodiment of this invention, during the test mode of operation of theapparatus, a laser beam whose power changes between at least twodifferent levels (for example, a recording level and an erasing level)is applied to a given-address position on the optical disc 22.

[0211] In the case where the optical disc 22 is of the phase changerewritable type, the power of the laser beam may change among areproducing level, an erasing level, and a recording level. In the casewhere the optical disc 22 is of the organic-dye recordable type, thepower of the laser beam may change between a reproducing level and arecording level.

[0212] The feedback signal outputted from the monitor diode indicatesthe measured power (the measured intensity) of the laser beam. Thefeedback signal is converted into corresponding digital data. The systemcontroller 12 derives, from the digital data, the measured valuescorresponding to the different power levels respectively. The systemcontroller 12 calculates the errors between the measured values andoptimal values. The system controller 12 controls the actual powerlevels of the laser beam so as to move the measured values toward theoptical values.

[0213] The fifteenth embodiment of this invention compensates for avariation in the laser power (the laser intensity) which might be causedby the temperature dependency and the ageing of the semiconductor laser.

[0214] The control in the fifteenth embodiment of this invention may becombined with the previously-mentioned control based on the asymmetrymeasurement or the jitter measurement.

[0215] The fifteenth embodiment of this invention uses a block SIZinstead of the block SI in FIGS. 14 and 15.

[0216] As shown in FIG. 23, the block SIZ has a first step SIA followingthe step SH (see FIG. 14). The step SIA detects the address of aposition (an ECC block) on the optical disc 22 which immediately followsthe address of the last accessed position loaded with the contents data.The ECC block address A2 in FIG. 12 corresponds to the address detectedby the step SIA while the ECC block address A1 in FIG. 12 corresponds tothe address of the last accessed position loaded with the contents data.

[0217] A step SIB subsequent to the step SIA controls the amplifier unit26 to record the test pattern signal on the disc position (the ECCblock) whose address is detected by the step SIA. During the recordingof the test pattern signal, the step SIB changes the power or theintensity of the laser beam between at least two different levels. Thestep SIB derives, from the feedback signal outputted by the monitordiode, the measured values corresponding to the different power levelsrespectively. The step SIB calculates the errors between the measuredvalues and optimal values.

[0218] A step SIC following the step SIB decides whether or not a set ofthe calculated errors is in a predetermined acceptable range. When theset of the calculated errors is in the acceptable range, the programadvances from the step SIC to the step SJ (see FIG. 14). When the set ofthe calculated errors is not in the acceptable range, the programadvances from the step SIC to a step SID.

[0219] The step SID outputs a control signal to the waveform correctioncircuit, thereby changing the waveform correction parameter orparameters in the direction of moving the measured power values towardthe optimal power values. After the step SID, the program advances tothe step SJ (see FIG. 14).

Sixteenth Embodiment

[0220] A sixteenth embodiment of this invention is a modification of oneof the first to fifteenth embodiments thereof. According to thesixteenth embodiment of this invention, during every free time of theoptical head 24 in the recording mode of operation of the apparatus, thewaveform correction optimizing process is implemented.

Seventeenth Embodiment

[0221] A seventeenth embodiment of this invention is a modification ofone of the first to sixteenth embodiments thereof. The seventeenthembodiment of this invention executes the waveform correction optimizingprocess without deciding whether or not the waveform correctionoptimizing process should be executed.

Eighteenth Embodiment

[0222] An eighteenth embodiment of this invention is a modification ofone of the first to seventeenth embodiments thereof. The eighteenthembodiment of this invention changes the waveform correction parametersfor determining the time intervals Ta, Th, Tc, and Td in accordance withthe temperature measured by the temperature sensor 36. For example, whenthe measured temperature is 10° C., the waveform correction parametersare changed so that the time interval Td will be increased relative tothe time interval Tc. When the measured temperature is 40° C., thewaveform correction parameters are changed so that the time interval Tcwill be increased relative to the time interval Td.

Nineteenth Embodiment

[0223] A nineteenth embodiment of this invention is a modification ofone of the first to eighteenth embodiments thereof. According to thenineteenth embodiment of this invention, during the test mode ofoperation of the apparatus, the highest-frequency signal “3T” isextracted from the reproduced RF signal. The waveform correctionparameters in the waveform correction circuit 60 are controlled so as tomaximize the amplitude of the highest-frequency signal “3T”.

Twentieth Embodiment

[0224] A twentieth embodiment of this invention is a modification of oneof the first to-nineteenth embodiments thereof. In the twentiethembodiment of this invention, the waveform correction optimizing processuses the jitter instead of the asymmetry. The twentieth embodiment ofthis invention includes a suitable circuit for counting the number oftimes of recording in connection with the recording track. The number oftimes of recording is incremented by “1” each time recording isexecuted. The eight different statuses P1, P2, . . . , and P8, amongwhich the power conditions of the laser beam are changed, are varied inthe direction of increasing the acceptable limit jitter value as thenumber of times of recording increases. It is preferable to change thetime intervals Ta, Tb, Tc, and Td on a stepwise basis. The twentiethembodiment of this invention compensates for an adverse change in jitterdue to an increase in the number of times of recording.

Twenty-First Embodiment

[0225] A twenty-first embodiment of this invention is a modification ofone of the first to twentieth embodiments thereof. In the twenty-firstembodiment of this invention, every signal pulse is shaped into a trainof short pulses based on the recording waveform WA independent of thedisc-scanning linear velocity. The amplitude of the pulse train (forexample, the amplitude of a front end portion of the pulse train) ischanged in accordance with the disc-scanning linear velocity. Thetwenty-first embodiment of this invention can provide a relatively greatphase margin.

Twenty-Second Embodiment

[0226] A twenty-second embodiment of this invention is a modification ofone of the first to twenty-first embodiments thereof. In thetwenty-second embodiment of this invention, every signal pulse is shapedinto a train of short pulses based on the recording waveform WAindependent of the disc-scanning linear velocity. The width of the shortpulses in the train is changed in accordance with the disc-scanninglinear velocity.

[0227] The twenty-second embodiment of this invention changes the laserbeam between a recording waveform WE of FIG. 24 and a recording waveformWF of FIG. 25 in accordance with the disc-scanning linear velocity. Asshown in FIG. 24, the recording waveform WE has a train of a first pulseand later pulses with a relatively small width. As shown in FIG. 25, therecording waveform WF has a train of a first pulse and later pulses witha relatively large width. The recording waveform WE is used for a lowlinear velocity while the recording waveform WF is used for a highlinear velocity. Since the heat accumulation effect is weaker as thedisc-scanning linear velocity rises, the large-width pulses in therecording waveform WF are prevented from causing an unwanted distortionin the shape of a recording mark.

[0228] The recording waveforms WE and WF may be modified as therecording waveform WC of FIG. 7 is designed. Specifically, in themodifications of the recording waveforms WE and WF, during a limitedtime interval immediately preceding each pulse train and a limited timeinterval immediately following the pulse train, the power of the laserbeam is lower than the erasing level Pb.

[0229] The recording waveforms WE and WF may be modified as therecording waveform WD of FIG. 8 is designed. Specifically, according tothe modifications of the recording waveforms WE and WF, in each pulsetrain, the power of a laser beam changes between a recording level Ppand a reproducing level (or a null level).

Twenty-Third Embodiment

[0230] A twenty-third embodiment of this invention is a modification ofone of the first to twenty-second embodiments thereof. The twenty-thirdembodiment of this invention is designed to properly operate on apartial ROM disc, a hybrid optical disc having an inner portion forminga ROM area and an outer portion forming a phase change RAM area, atwo-layer optical disc having one phase change recording film, atwo-layer optical disc having two phase change recording films, atwo-layer optical disc having one read only layer, or an optical dischaving two or more layers.

[0231] The twenty-third embodiment of this invention includes a devicefor detecting a multi-layer optical disc, a device for detecting that atleast one layer of a multi-layer optical disc is a recordable layer (ora rewritable layer), and a focus jump device for focusing the laser beamon the signal surface of selected one of layers in a multi-layer opticaldisc. In the twenty-third embodiment of this invention, the waveformcorrection values for the layers are decided during the test mode ofoperation of the apparatus, and the signals of the decided waveformcorrection values are stored.

Twenty-Fourth Embodiment

[0232] A twenty-fourth embodiment of this invention is a modification ofone of the first to twenty-third embodiments thereof. The twenty-fourthembodiment of this invention provides an optical disc drive apparatuswhich does not have any signal compressing/expanding circuit. Examplesof the optical disc drive apparatus are computer peripheral apparatusessuch as a DVD-RAM drive apparatus and a DVD-RW drive apparatus.

[0233] Compressed data are outputted from the optical disc driveapparatus to an external computer without being expanded. Then, thecompressed data are expanded in the external computer according tosoftware. The optical disc drive apparatus and the external computer areconnected by a bus of, for example, an ATAPI type or a IEEE1394 type.

[0234] In the optical disc drive apparatus, a suitable device monitorsthe state of the optical head 24, and decides which of a recordingstate, a reproducing state, a seek state, a busy state, and anunselected state the optical head 24 assumes. When the optical head 24falls into the unselected state, the waveform correction optimizingprocess is executed.

[0235] When the drive of the optical disc 22 has been started, the typeof the optical disc 22 is decided on the basis of the conditions of discinsertion and the conditions of turning on the power supply.Specifically, a decision is made as to whether the optical disc 22 has asingle layer or multiple layers. In addition, a decision is made as towhether or not the optical disc 22 has a recordable layer (a rewritablelayer). In the case where the optical disc 22 has a recordable layer (arewritable layer), a decision is made as to whether or the waveformcorrection optimizing process should be executed.

[0236] For example, a flag is used as an indication of whether or thewaveform correction optimizing process should be executed. The flag in alogic state of “0” indicates that the waveform correction optimizingprocess should be executed. The flag in a logic state of “1” indicatesthat the waveform correction optimizing process should not be executed.When the power supply is turned on or the optical disc 22 is insertedinto the apparatus, the flag is in a logic state of “0”. Thus, at thistime, by referring to the flag, it is decided that the waveformcorrection optimizing process should be executed. Therefore, thewaveform correction optimizing process is actually executed. Then, theflag is changed to a logic state of “1”.

[0237] When a predetermined time has elapsed since the moment of thelast execution of the waveform correction optimizing process, the flagis returned to a logic state of “0”. When the present temperaturediffers from that occurring at the moment of the last execution of thewaveform correction optimizing process by more than a predeterminedvalue, the flag is returned to a logic state of “0”.

[0238] In the case where the optical disc 22 has a recordable layer (arewritable layer), detection is given of whether or not the optical head24 falls into the unselected state. When the flag is in a logic state of“0” and the optical head 24 falls into the unselected state, thewaveform correction optimizing process is executed.

[0239] The optical disc drive apparatus includes a focus jump device forfocusing the laser beam on the signal surface of selected one of layersin the optical disc 22. In the optical disc drive apparatus, thewaveform correction values for the layers are decided during the testmode of operation of the apparatus, and the signals of the decidedwaveform correction values are stored.

Twenty-fifth Embodiment

[0240] A twenty-fifth embodiment of this invention is a modification ofone of the first to twenty-fourth embodiments thereof. In thetwenty-fifth embodiment of this invention, the optical disc 22 is of theDVD type. An innermost portion of the optical disc has a lead-in area.The outer edge of the innermost portion of the optical disc has a radiusof 24 mm. A major portion of the optical disc 22 which extends radiallyoutward of the innermost portion is used as a data area.

[0241] The lead-in area of the optical disc 22 stores physicalinformation representing the disc type, the layer condition, thereflectivity, the data start address, and the data end address. The disctype means the read only type, the write once type, or the rewritabletype. The layer condition means the single-layer disc, the two-layerdisc, “parallel”, or “opposite”. The reflectivity is equal to 0.7 in thecase of the single-layer disc. The reflectivity is equal to 0.3 in thecase of the two-layer disc.

[0242] In addition, the lead-in area of the optical disc 22 stores thefollowing information pieces {circle over (1)}-{circle over (6)}. Theinformation piece {circle over (1)} indicates the optimal recordingpower level Pp and the optimal erasing power level Pb of the laser beam(see FIG. 3). The information piece {circle over (2)} indicates theoptimal time intervals Ta, Tb, Tc, and Td (see FIG. 3). The informationpiece {circle over (2)} may indicate the optimal values of the waveformcorrection parameters in the waveform correction circuit 60 whichdetermine the time intervals Ta, Th, Tc, and Td. The information piece{circle over (3)} indicates the disc-scanning linear velocity and thetemperature at which the waveform correction optimizing process wasexecuted. The information piece {circle over (4)} indicates theidentification code word (ID) of the recording apparatus. Theinformation piece {circle over (5)} indicates the disc maker. Theinformation piece {circle over (5)} may further indicate the maker ofthe recording apparatus. The information piece {circle over (6)}indicates the production lot number of the disc. The information piece{circle over (6)} may further indicate the disc maker and the recordingapparatus maker.

[0243] The lead-in area of the optical disc 22 may store an encryptedversion of the information pieces {circle over (1)}-{circle over (6)}.In the case where the optical disc 22 has two or more layers, only oneof the layers may store the information pieces {circle over (1)}-{circleover (6)}.

[0244] The lead-in area of the optical disc 22 includes a test recordingarea on which the test pattern signal is recorded during the waveformcorrection optimizing process. The test recording area may be locatedoutside the lead-in area.

[0245] When the optical disc 22 is placed in the apparatus and the driveof the optical disc 22 is started, a signal is reproduced from thelead-in area thereof. The information pieces {circle over (1)}-{circleover (6)} are extracted from the reproduced signal. During laterrecording, the apparatus uses the optimal waveform correction valuesindicated by the information pieces {circle over (1)} and {circle over(2)}. The optimal waveform correction values mean the optimal recordingpower level Pp and the optimal erasing power level Pb of the laser beam,and the optimal time intervals Ta, Th, Tc, and Td. The optimal waveformcorrection values may mean the optimal values of the waveform correctionparameters in the waveform correction circuit 60 which determine thetime intervals Ta, Th, Tc, and Td. The way of use of the optimalwaveform correction values is changed in response to the disc maker, thereproduction lot number of the disc, and the recording apparatus makerindicated by the information pieces {circle over (5)} and {circle over(6)}. On the other hand, in the absence of the information pieces{circle over (1)} and {circle over (2)} from the reproduced signal, thewaveform correction optimizing process is executed to determine theoptimal waveform correction values (the optimal values of the waveformcorrection parameters).

[0246] Signals of the optimal waveform correction values are encodedinto the information pieces {circle over (1)} and {circle over (2)}.Then, the information pieces {circle over (1)} and {circle over (2)} arerecorded on the lead-in area of the optical disc 22.

[0247] During the execution of the waveform correction optimizingprocess, the temperature is measured via the temperature sensor 36. Asignal of the measured temperature and a signal of the disc-scanninglinear velocity are encoded into the information piece {circle over(3)}. The information piece {circle over (3)} is recorded on the lead-inarea of the optical disc 22 while the information pieces {circle over(1)} and {circle over (2)} are recorded thereon.

[0248] As previously mentioned, when the optical disc 22 is placed inthe apparatus and the drive of the optical disc 22 is started, a signalis reproduced from the lead-in area thereof. The information pieces{circle over (1)}-{circle over (6)} are extracted from the reproducedsignal. Immediately before the start of later recording, the temperatureis measured via the temperature sensor 36. Calculation is made as to thedifference between the present temperature and the temperature indicatedby the information piece {circle over (3)}. Also, calculation is made asto the difference between the currently-set linear velocity and thelinear velocity indicated by the information piece {circle over (3)}.The optimal waveform correction values (the optimal values of thewaveform correction parameters) are revised on the basis of thecalculated temperature difference and the calculated linear-velocitydifference according to a calculation process or a table look-upprocess. The revision-resultant optimal waveform correction values areused in later recording.

Twenty-Sixth Embodiment

[0249] A twenty-sixth embodiment of this invention is a modification ofthe twenty-fifth embodiment thereof. In the twenty-sixth embodiment ofthis invention, the optical disc 22 has first and second recordinglayers. The first recording layer includes a specified area for storingthe physical information, the information pieces {circle over(1)}-{circle over (6)} related to the first recording layer, and theinformation pieces {circle over (1)}-{circle over (6)} related to thesecond recording layer.

[0250] When the optical disc 22 is placed in the apparatus and the driveof the optical disc 22 is started, a signal is reproduced from thespecified area of the first recording layer thereof. The informationpieces {circle over (1)}-{circle over (6)} related to the firstrecording layer, and the information pieces {circle over (1)}-{circleover (6)} related to the second recording layer are extracted from thereproduced signal. During later recording on the first recording layerof the optical disc 22, the apparatus uses the optimal waveformcorrection values indicated by the information pieces {circle over (1)}and {circle over (2)} related to the first recording layer. During laterrecording on the second recording layer of the optical disc 22, theapparatus uses the optimal waveform correction values indicated by theinformation pieces {circle over (1)} and {circle over (2)} related tothe second recording layer. On the other hand, in the absence of thetwo-layer-related information pieces {circle over (1)} and {circle over(2)} from the reproduced signal, the waveform correction optimizingprocess is executed on the first recording layer to determine theoptimal waveform correction values (the optimal values of the waveformcorrection parameters) related to the first recording layer. Then, focusjump to the second recording layer is implemented, and the waveformcorrection optimizing process is executed on the second recording layerto determine the optimal waveform correction values related to thesecond recording layer. Signals of the optimal waveform correctionvalues related to the first and second recording layers are encoded intothe two-layer-related information pieces {circle over (1)} and {circleover (2)}. Then, the two-layer-related information pieces {circle over(1)} and {circle over (2)} are recorded on the specified area of thefirst recording layer of the optical disc 22.

Twenty-Seventh Embodiment

[0251] A twenty-seventh embodiment of this invention is based on acombination of at least two of the first to twenty-sixth embodimentsthereof. The twenty-seventh embodiment of this invention selectivelyuses at least one of the evaluation method “A”, the evaluation method“B”, and the evaluation method “C” as a part of the waveform correctionoptimizing process. In the evaluation method “A”, the test patternsignal having the alternation of the lowest-frequency signal “11T” andthe highest-frequency signal “3T” is recorded on the optical disc 22,and the test pattern signal is reproduced therefrom. The asymmetries ofrespective time segments of the reproduced test pattern signal aremeasured.

[0252] In the evaluation method “B”, the random signal is recorded onthe optical disc 22 as the test pattern signal, and the random signal isreproduced therefrom. The jitters of the reproduced random signal aremeasured.

[0253] In the evaluation method “C”, the feedback signal outputted fromthe monitor diode is measured while the power of the laser beam ischanged among the reproducing level, the erasing level, and therecording level.

[0254]FIG. 26 is a flowchart of a segment of a program for the systemcontroller 12. The program segment in FIG. 26 is executed when the driveof the optical disc 22 is started. With reference to FIG. 26, a firststep SKa of the program segment detects the type of the optical disc 22.For example, the step SKa measures the reflectivity of the optical disc22, and decides the type of the optical disc 22 on the basis of themeasured reflectivity.

[0255] A step SKb following the step SKa selects at least one from amongthe evaluation methods “A”, “B”, and “C”. The step SKb executes thewaveform correction optimizing process in accordance with the selectedevaluation method (or the selected evaluation methods).

[0256] In the case where the type of the optical disc 22 is the DVDRWtype (the phase change rewritable type), the evaluation methods “B” and“C” are selected. In this case, only the evaluation method “B” may beselected. In the case where the type of the optical disc 22 is the DVD-Rtype (the organic-dye recordable type), the evaluation methods “A” and“C” are selected. In this case, only the evaluation method “A” may beselected.

Twenty-Eighth Embodiment

[0257] A twenty-eighth embodiment of this invention is a modification ofthe twenty-seventh embodiment thereof. In the twenty-eighth embodimentof this invention, when a disc position to be accessed at this time isseparate from the disc position previously accessed for data recordingby shorter than a predetermined distance, the evaluation method “C” isselected. When the lapse of time since the previous recording is shorterthan a predetermined time interval, the evaluation method “C” isselected. When a disc position to be accessed at this time is separatefrom the disc position previously accessed for data recording by atleast the predetermined distance, the evaluation method “A” or “B” isselected. When the lapse of time since the previous recording is equalto or longer than the predetermined time interval, the evaluation method“A” or “B” is selected.

Twenty-Ninth Embodiment

[0258] A twenty-ninth embodiment of this invention is a modification ofthe twenty-seventh embodiment thereof. In the twenty-ninth embodiment ofthis invention, the optical disc 22 has a specified area for storingdisc intrinsic information (disc ID information). The disc intrinsicinformation represents the disc maker, the disc type, the disc articlenumber, and the disc production lot number. The memory in the systemcontroller 12 stores a table signal indicating the relation of the discintrinsic information with the evaluation methods “A”, “B”, and “C”.

[0259]FIG. 27 is a flowchart of a segment of a program for the systemcontroller 12. The program segment in FIG. 27 is executed when the driveof the optical disc 22 is started. With reference to FIG. 27, a firststep SKA of the program segment reproduces a signal from the specifiedarea of the optical disc 22.

[0260] A step SKB following the step SKA extracts the disc intrinsicinformation from the reproduced signal.

[0261] A step SKC subsequent to the step SKB selects at least one fromamong the evaluation methods “A”, “B”, and “C” by referring to the tablesignal. The step SKC executes the waveform correction optimizing processin accordance with the selected evaluation method (or the selectedevaluation methods).

Thirtieth Embodiment

[0262] A thirtieth embodiment of this invention is a modification of oneof the first to twenty-ninth embodiments thereof. In the thirtiethembodiment of this invention, the test pattern generation circuit 64 isdesigned so that the test pattern signal can be shifted along a timebase relative to the test ECC block by a variable quantity (a variabletime interval). The shift quantity may be fixed to, for example, about 6bytes measured in unit of the recording clock signal (the bit clocksignal). The shift quantity may be variable in a range around 6 bytesmeasured in unit of the recording clock signal.

[0263] The shift quantity can be set by the system controller 12. In thecase where the test pattern signal is recorded on an area of the opticaldisc 22 for the first time, the system controller 12 sets the shiftquantity to “0”. In the case where the test pattern signal is recordedagain on an area of the optical disc 22 which was loaded with the testpattern signal, the system controller 12 generates a random signal. Thesystem controller 12 sets the shift quantity to the random valuerepresented by the random signal. The test pattern signal is shifted bythe quantity set by the system controller 12. The test pattern signal isrecorded. The test pattern signal is reproduced at timings shifted fromthe original timings by a quantity corresponding to the quantity set bythe system controller 12. The asymmetries of respective time segments ofthe reproduced test pattern signal are measured.

Thirty-First Embodiment

[0264] A thirty-first embodiment of this invention is a modification ofone of the first to thirtieth embodiments thereof. In the thirty-firstembodiment of this invention, the test pattern generation circuit 64 isdesigned so that the lowest-frequency signal “11T” and thehighest-frequency signal “3T” can be exchanged in time position in thetest pattern signal.

[0265] In the case where the test pattern signal is recorded on an areaof the optical disc 22 for the first time, the lowest-frequency signal“11T” and the highest-frequency signal “3T” are arranged in the testpattern signal in the order shown in FIG. 12. In the case where the testpattern signal is recorded again on an area of the optical disc 22 whichwas loaded with the test pattern signal, the lowest-frequency signal“11T” and the highest-frequency signal “3T” are arranged in the testpattern signal in the order opposite to that shown in FIG. 12. In thiscase, the highest-frequency signal “3T” is recorded on the first sector,that is, the B0 sector in the ECC block.

[0266] The lowest-frequency signal “11T” is recorded on the secondsector, that is, the B1 sector in the ECC block. Similarly, the signalarrangement is changed between the two different orders during laterrecording of the test pattern signal.

Thirty-Second Embodiment

[0267] A thirty-second embodiment of this invention is a modification ofone of the twenty-seventh, twenty-eighth, and twenty-ninth embodimentsthereof. In the thirty-second embodiment of this invention, during thefirst execution of the waveform correction optimizing process based onthe evaluation method “C”, the feedback signal outputted from themonitor diode is measured while the power (the intensity) of the laserbeam is set to the erasing level and is then changed to the recordinglevel. During the second execution of the waveform correction optimizingprocess based on the evaluation method “C”, the feedback signaloutputted from the monitor diode is measured while the power (theintensity) of the laser beam is set to the recording level and is thenchanged to the erasing level. Similarly, the arrangement of the powerlevels is changed between the two different orders during the laterexecution of the waveform correction optimizing process.

Thirty-Third Embodiment

[0268] A thirty-third embodiment of this invention is a modification ofone of the first to thirty-second embodiments thereof. In thethirty-third embodiment of this invention, the optical disc 22 has apredetermined area exclusively for storing the test pattern signal.

Thirty-Fourth Embodiment

[0269] A thirty-fourth embodiment of this invention is a modification ofthe thirty-third embodiment thereof. In the thirty-fourth embodiment ofthis invention, when the optical disc 22 is placed in the apparatus andthe drive of the optical disc 22 is started, the test pattern signal isrecorded on the exclusive area of the optical disc 22 and the waveformcorrection optimizing process is executed. During later recording, thewaveform correction optimizing process is executed while the testpattern signal is recorded on an area of the optical disc which isassigned to contents data.

Thirty-Fifth Embodiment

[0270] A thirty-fifth embodiment of this invention is a modification ofone of the twenty-seventh, twenty-eighth, twenty-ninth, andthirty-second embodiments thereof. The thirty-fifth embodiment of thisinvention executes the waveform correction optimizing process whilecombining at least two of the evaluation methods “A”, “B”, and “C” andimplementing the combined evaluation methods.

What is claimed is:
 1. An apparatus for recording and reproducing aninformation signal on and from an optical disc, comprising: a memory;means for writing the information signal into the memory; means forreading out the information signal from the memory; an optical head forgenerating a laser beam in response to the readout information signal,and applying the laser beam to the optical disc to record the readoutinformation signal on the optical disc; means for recording a testsignal on a position of the optical disc near a recording positionthereof via the optical head during the writing of the informationsignal into the memory; means for reproducing the test signal from theoptical disc; means for evaluating the reproduced test signal togenerate an evaluation result; and means for optimizing an intensity ofthe laser beam in response to the evaluation result.
 2. An apparatus forrecording and reproducing an information signal on and from an opticaldisc, comprising: a memory; means for writing the information signalinto the memory; means for reading out the information signal from thememory; an optical head for generating a laser beam in response to thereadout information signal, and applying the laser beam to the opticaldisc to record the readout information signal on the optical disc; meansfor changing a power of the laser beam among a plurality of differentlevels; means for measuring the laser beam to generate measurementresult values during the change of the power of the laser beam among theplurality of the different levels; and means for optimizing an intensityof the laser beam in response to the measurement result values.
 3. Anapparatus as recited in claim 1, wherein the test signal comprises atest pattern signal, and the recording means comprises means forrecording the test pattern signal on the optical disc via the opticalhead while changing an intensity of the laser beam among a plurality ofdifferent levels for a testing purpose, and wherein the reproducingmeans comprises means for reproducing the test pattern signal from theoptical disc, and the evaluating means comprises means for evaluating atleast one of asymmetry and jitter of the reproduced test pattern signalto generate the evaluation result.
 4. An apparatus as recited in claim2, further comprising means for repetitively measuring the laser beam torepetitively generate a measurement result value, means for calculatinga difference between a current measurement result value and animmediately preceding measurement result value, and means for enablingthe optimizing means to optimize the intensity of the laser beam whenthe calculated difference is equal to or greater than a predeterminedvalue.
 5. An apparatus as recited in claim 1, further comprising meansfor repetitively measuring a temperature to repetitively generate ameasured temperature value, means for calculating a difference between acurrent measured temperature value and an immediately preceding measuredtemperature value, and means for enabling the optimizing means tooptimize the intensity of the laser beam when the calculated differenceis equal to or greater than a predetermined value.
 6. An apparatus asrecited in claim 1, further comprising means for measuring a lapse oftime since a moment of the last optimization of the intensity of thelaser beam, and for deciding whether or not the measured lapse of timeexceeds a predetermined time to generate a decision result, and meansfor optimizing the intensity of the laser beam in response to thedecision result.
 7. An apparatus as recited in claim 1, furthercomprising means for measuring a distance between a current recordingposition and a next recording position on the optical disc, and decidingwhether or not the measured distance exceeds a predetermined distance togenerate a decision result, and means for optimizing the intensity ofthe laser beam in response to the decision result.
 8. A method ofrecording and reproducing an information signal on and from an opticaldisc, comprising the steps of: writing an information signal into amemory; reading out the information signal from the memory; generating alaser beam in response to the readout information signal, and applyingthe laser beam to the optical disc to record the readout informationsignal on the optical disc; recording a test signal on a position of theoptical disc near a recording position thereof via the optical headduring the writing of the information signal into the memory;reproducing the test signal from the optical disc; evaluating thereproduced test signal to generate an evaluation result; and optimizingan intensity of the laser beam in response to the evaluation result. 9.An optical disc having an area storing information of an intensity of alaser beam which has been optimized by the apparatus of claim
 1. 10. Anapparatus for recording and reproducing an information signal on andfrom an optical disc, comprising: a memory; means for writing theinformation signal into the memory; means for reading out theinformation signal from the memory; an optical head for generating alaser beam in response to the readout information signal, and applyingthe laser beam to the optical disc to record the readout informationsignal on the optical disc; means for recording a test signal on aposition of the optical disc near a recording position thereof via theoptical head during the writing of the information signal into thememory; means for reproducing the test signal from the optical disc;first optimizing means for measuring asymmetry of the reproduced testsignal, and optimizing an intensity of the laser beam in response to themeasured asymmetry; second optimizing means for measuring jitter of thereproduced test signal, and optimizing the intensity of the laser beamin response to the measured jitter; third optimizing means for measuringthe laser beam to generate a measurement result, and optimizing theintensity of the laser beam in response to the measurement result; meansfor detecting a type of the optical disc; and means for selecting atleast one of the first, second, and third optimizing means in responseto the detected type, and enabling the selected one of the first,second, and third optimizing means.
 11. An apparatus as recited in claim10, wherein the type detecting means comprises means for decidingwhether the type of the optical disc is an organic-dye type or a phasechange type to generate a type decision result, and the selecting meanscomprises means for selecting at least one of the first, second, andthird optimizing means in response to the type decision result, andenabling the selected one of the first, second, and third optimizingmeans.
 12. An apparatus as recited in claim 10, wherein the typedetecting means comprises means for reproducing disc information fromthe optical disc, and means for deriving a disc maker from thereproduced disc information, and wherein the selecting means comprisesmeans for selecting at least one of the first, second, and thirdoptimizing means in response to the disc maker, and enabling theselected one of the first, second, and third optimizing means.
 13. Anapparatus as recited in claim 10, wherein the type detecting meanscomprises means for reproducing disc information from the optical disc,and means for deriving a disc article number from the reproduced discinformation, and wherein the selecting means comprises means forselecting at least one of the first, second, and third optimizing meansin response to the disc article number, and enabling the selected one ofthe first, second, and third optimizing means.
 14. An apparatus asrecited in claim 10, wherein the type detecting means comprises meansfor reproducing disc information from the optical disc, and means forderiving a disc production lot number from the reproduced discinformation, and wherein the selecting means comprises means forselecting at least one of the first, second, and third optimizing meansin response to the disc production lot number, and enabling the selectedone of the first, second, and third optimizing means.
 15. An apparatusfor recording and reproducing an information signal on and from anoptical disc, comprising: a memory; means for writing the informationsignal into the memory; means for reading out the information signalfrom the memory; an optical head for generating a laser beam in responseto the readout information signal, and applying the laser beam to theoptical disc to record the readout information signal on the opticaldisc; means for repetitively recording a test signal on a place on theoptical disc via the optical head, the place being near a recordingposition of the optical disc which is subjected to signal recordingnext; means for reproducing the test signal from the optical disc; meansfor evaluating the reproduced test signal to generate an evaluationresult; means for optimizing an intensity of the laser beam in responseto the evaluation result; and means for changing the test signal on arecording-by-recording basis.
 16. An apparatus as recited in claim 15,wherein the changing means comprises means for generating a randomsignal providing a random timing, and means for shifting the test signalin response to the random timing to change the test signal on therecording-by-recording basis.
 17. An apparatus as recited in claim 15,wherein the changing means comprises means for time-positionallyexchanging signal segments of the test signal to change the test signalon the recording-by-recording basis.
 18. An apparatus for recording andreproducing an information signal on and from an optical disc,comprising: means for generating a laser beam in response to a firsttime segment of the information signal, and applying the laser beam to afirst place on the optical disc to record the first time segment of theinformation signal on the first place on the optical disc; means forgenerating a laser beam in response to a test signal, and applying thelaser beam to a second place on the optical disc to record the testsignal on the second place on the optical disc while changing the laserbeam among a plurality of conditions different from each other, thesecond place immediately following the first place; means forreproducing the test signal from the optical disc; means for evaluatingthe reproduced test signal to generate evaluation results correspondingto the respective different conditions of the laser beam; means fordeciding a best of the evaluation results; and means for generating alaser beam in one of the different conditions which corresponds to thebest evaluation result and in response to a second time segment of theinformation signal, and applying the laser beam to the second place onthe optical disc to write the second time segment of the informationsignal over the test signal on the second place on the optical disc, thesecond time segment immediately following the first time segment.
 19. Anapparatus as recited in claim 18, wherein the different conditions ofthe laser beam comprise different conditions of pulses in pulse trainsof the laser beam.
 20. An apparatus for recording and reproducing aninformation signal on and from an optical disc, comprising: a memory;means for writing the information signal into the memory; means forreading out the information signal from the memory; an optical head forgenerating a laser beam in response to the readout information signal,and applying the laser beam to the optical disc to record the readoutinformation signal on the optical disc; means for recording a testsignal on the optical disc via the optical head while changing the laserbeam among a plurality of conditions different from each other for atesting purpose during the writing of the information signal into thememory; means for reproducing the test signal from the optical disc;means for evaluating the reproduced test signal to generate evaluationresults corresponding to the respective different conditions of thelaser beam; means for deciding a best of the evaluation results; andmeans for controlling the laser beam into one of the differentconditions which corresponds to the best evaluation result.
 21. Anapparatus as recited in claim 20, wherein the different conditions ofthe laser beam comprise different conditions of pulses in pulse trainsof the laser beam.